Programming Courses | Courses | archita phukan | Love Babbar | Coding Ninja | Durgasoft | ChatGPT prompt AI Prompt
3.54K subscribers
705 photos
15 videos
1 file
155 links
Programming
Coding
AI Websites

📡Network of #TheStarkArmy©

📌Shop : https://t.me/TheStarkArmyShop/25

☎️ Paid Ads : @ReachtoStarkBot

Ads policy : https://bit.ly/2BxoT2O
Download Telegram
🔰 5 Useful web APIs

@CodingCoursePro
Shared with Love
Please open Telegram to view this post
VIEW IN TELEGRAM
Please open Telegram to view this post
VIEW IN TELEGRAM
3
🚀 Top Web Development Frameworks You Should Know 🌐🔥

⚛️ React
✔️ Component-Based UI
✔️ Fast & Interactive Websites
✔️ Huge Ecosystem
✔️ Best for Frontend Development

🟩 Next.js
✔️ SEO Friendly Apps
✔️ Server-Side Rendering
✔️ Full Stack Features
✔️ High Performance Websites

🅰️ Angular
✔️ Enterprise Applications
✔️ TypeScript Support
✔️ Powerful Architecture
✔️ Scalable Frontend Apps

🟢 Vue.js
✔️ Beginner Friendly
✔️ Lightweight Framework
✔️ Fast Learning Curve
✔️ Flexible UI Development

🚀 Node.js + Express.js
✔️ Backend APIs
✔️ Real-Time Applications
✔️ Full Stack JavaScript
✔️ REST API Development

🐍 Django
✔️ Secure Web Applications
✔️ Built-in Authentication
✔️ Fast Backend Development
✔️ Python-Based Framework

⚡️ FastAPI
✔️ High-Speed APIs
✔️ AI & ML Backend
✔️ Automatic Documentation
✔️ Async Support

☕️ Spring Boot
✔️ Enterprise Backend Apps
✔️ Microservices
✔️ Banking & Large Systems
✔️ Secure APIs

🎨 CSS Frameworks to Learn
✔️ Tailwind CSS
✔️ Bootstrap
✔️ Material UI

💡 Frameworks help developers build faster, cleaner, and scalable applications.

💬 Tap ❤️ if this helped you!

@CodingCoursePro
Shared with Love
Please open Telegram to view this post
VIEW IN TELEGRAM
1
🎯 💻 Coding Interview Questions (With Answers)

🧠 1️⃣ Tell me about yourself
Sample Answer:
"I have 4+ years as a software engineer specializing in full-stack development and algorithms. I've built scalable systems handling 1M+ daily users at a fintech startup using MERN stack and microservices. Expert in JavaScript/Python, system design, and competitive programming (LeetCode 2000+/2800). I love writing clean, testable code and optimizing for performance under scale."

📊 2️⃣ What is the difference between a stack and a queue?
Answer:
A stack follows LIFO (Last In, First Out) principle with operations push (add to top) and pop (remove from top). Use cases: function call stack, undo/redo features.
A queue follows FIFO (First In, First Out) with enqueue (add to rear) and dequeue (remove from front). Use cases: breadth-first search, task scheduling, printers.
Both O(1) operations with arrays/linked lists.

🔗 3️⃣ What is the difference between time complexity and space complexity?
Answer:
Time complexity measures how runtime grows with input size n (e.g., O(n²) quadratic loops).
Space complexity measures memory usage growth (e.g., O(n) array stores all elements).
Tradeoffs exist: recursion uses stack space O(n), iteration uses O(1). Always analyze both.

🧠 4️⃣ How do you find duplicates in an array?
Answer:
Optimal: Hash Set O(n) time/space
function findDuplicates(arr) {
const seen = new Set();
const dups = new Set();
for (let num of arr) {
if (seen.has(num)) dups.add(num);
else seen.add(num);
}
return Array.from(dups);
}

Space optimized: Sort O(n log n) then scan adjacent equals.

📈 5️⃣ What is binary search and when would you use it?
Answer:
Binary search finds target in sorted array in O(log n) by repeatedly dividing search interval in half:
mid = (left + right) / 2
If arr[mid] == target return mid
If arr[mid] < target search right half
Else search left half
Use when: Data naturally sorted or sorting cost acceptable. Iterative version avoids recursion stack overflow.

📊 6️⃣ How do you reverse a linked list?
Answer:
Iterative O(n) solution flipping next pointers:
function reverseList(head) {
let prev = null, curr = head;
while (curr) {
let nextTemp = curr.next;
curr.next = prev;
prev = curr;
curr = nextTemp;
}
return prev;
}

Recursive: reverseList(curr.next).then(curr.next.prev = curr, curr.next = null).

📉 7️⃣ What is recursion and why is the base case important?
Answer:
Recursion is a function calling itself with modified arguments until base case stops it. Without base case → stack overflow.
Example Fibonacci:
function fib(n) {
if (n <= 1) return n; // Base case
return fib(n-1) + fib(n-2);
}

Memoization optimizes overlapping subproblems.

📊 8️⃣ How do you merge two sorted arrays?
Answer:
Two-pointer technique O(n+m):
function mergeSorted(a1, a2) {
let i=0, j=0, result = [];
while (i < a1.length && j < a2.length) {
if (a1[i] < a2[j]) result.push(a1[i++]);
else result.push(a2[j++]);
}
return result.concat(a1.slice(i)).concat(a2.slice(j));
}

Handles unequal lengths cleanly.

🧠 9️⃣ How do you detect a cycle in a linked list?
Answer:
Floyd's Tortoise & Hare: Slow moves 1 step, fast moves 2. If they meet → cycle.
To find start: Reset slow to head, move both 1 step until meet.
function hasCycle(head) {
let slow = head, fast = head;
while (fast && fast.next) {
slow = slow.next;
fast = fast.next.next;
if (slow === fast) return true;
}
return false;
}

Double Tap ❤️ For More
5
🚀 Complete Next.js Roadmap 🌐🔥

🧠 STEP 1: Learn JavaScript Fundamentals
Variables & Functions
ES6 Features
Arrays & Objects
Async/Await
DOM Manipulation

🛠 Concepts to Learn:
Arrow Functions
Destructuring
Promises
Modules

⚛️ STEP 2: Learn React Basics
JSX
Components
Props & State
Event Handling
React Hooks

🛠 Hooks to Learn:
useState
useEffect
useContext
useRef

🚀 STEP 3: Understand Next.js Basics
What is Next.js?
File-Based Routing
Pages & Layouts
App Router
Server Components

🛠 Tools to Learn:
Next.js
React
Node.js

🌐 STEP 4: Learn Routing & Navigation
Dynamic Routes
Nested Routes
Route Groups
Navigation Components

🛠 Features to Learn:
Link Component
useRouter
Middleware

STEP 5: Learn Data Fetching
Server-Side Rendering (SSR)
Static Site Generation (SSG)
Incremental Static Regeneration (ISR)
API Routes

🛠 APIs & Tools:
Fetch API
Axios
REST APIs
GraphQL Basics

🎨 STEP 6: Learn Styling & UI
CSS Modules
Tailwind CSS
Responsive Design
UI Components

🛠 Frameworks to Learn:
Tailwind CSS
Material UI
shadcn/ui

🔐 STEP 7: Learn Authentication & Databases
User Authentication
JWT & Sessions
Database Integration
Protected Routes

🛠 Tools to Learn:
NextAuth.js
Prisma
MongoDB
PostgreSQL

☁️ STEP 8: Learn Deployment
Build Optimization
SEO Optimization
Environment Variables
CI/CD Basics

🛠 Platforms to Learn:
Vercel
Netlify
Docker

🔥 STEP 9: Build Real Next.js Projects
Portfolio Website
AI SaaS Dashboard
Blog Platform
E-commerce Website
Chat Application

💡 The best way to master Next.js:
👉 Learn React → Build Pages → Work with APIs → Deploy Real Projects

💬 Tap ❤️ if this helped you!
1
Double Tap ❤️ For More

@CodingCoursePro
Shared with Love
Please open Telegram to view this post
VIEW IN TELEGRAM
5
AI Models and their Country of Origin

• ChatGPT - 🇺🇸 United States (OpenAI)
• Claude - 🇺🇸 United States (Anthropic)
• Gemini - 🇺🇸 United States (Google)
• Grok - 🇺🇸 United States (xAI)
• Llama - 🇺🇸 United States (Meta)
• Mistral - 🇫🇷 France (Mistral AI)
• DeepSeek - 🇨🇳 China (DeepSeek AI)
• Qwen - 🇨🇳 China (Alibaba)
• ERNIE - 🇨🇳 China (Baidu)
• Falcon - 🇦🇪 United Arab Emirates
• Sarvam-1 - 🇮🇳 India (Sarvam AI)
• Krutrim LLM - 🇮🇳 India (Krutrim)

@CodingCoursePro
Shared with Love
Please open Telegram to view this post
VIEW IN TELEGRAM
🚀 Complete Angular Roadmap 🅰️🔥

🧠 STEP 1: Learn Web Development Basics
HTML Fundamentals
CSS & Responsive Design
JavaScript Basics
ES6 Features
TypeScript Basics

🛠 Concepts to Learn:
Functions & Objects
DOM Manipulation
Async JavaScript
Modules

STEP 2: Learn TypeScript
Types & Interfaces
Classes & OOP
Generics
Decorators
Modules & Imports

🛠 Tools to Learn:
TypeScript
Visual Studio Code

🅰️ STEP 3: Learn Angular Basics
Angular Architecture
Components
Modules
Templates
Data Binding

🛠 Frameworks & Tools:
Angular
Angular CLI
Node.js

📊 STEP 4: Learn Components & Routing
Reusable Components
Routing & Navigation
Route Parameters
Lazy Loading
Nested Routes

🛠 Features to Learn:
Router Module
Services
Dependency Injection

STEP 5: Learn Forms & APIs
Template-Driven Forms
Reactive Forms
Form Validation
REST API Integration
HTTP Requests

🛠 Libraries to Learn:
HttpClient
RxJS
Axios Basics

🎨 STEP 6: Learn Styling & UI
Angular Material
Bootstrap
Tailwind CSS
Responsive UI Design

🛠 UI Libraries:
Angular Material
Bootstrap
Tailwind CSS

🔐 STEP 7: Learn Advanced Angular
State Management
Authentication
Guards & Interceptors
Performance Optimization
Unit Testing

🛠 Advanced Tools:
NgRx
JWT Authentication
Jasmine & Karma

☁️ STEP 8: Learn Deployment
Production Builds
Environment Variables
CI/CD Basics
Hosting Angular Apps

🛠 Platforms to Learn:
Firebase
Netlify
Docker

🔥 STEP 9: Build Real Angular Projects
Portfolio Website
Admin Dashboard
E-commerce App
Task Management App
Chat Application

💡 The best way to master Angular:
👉 Learn TypeScript → Build Components → Work with APIs → Create Real Projects

💬 Tap ❤️ if this helped you!
1
🚀 Complete MERN Stack Roadmap 👨‍💻🔥

The MERN Stack is one of the most popular technologies for building modern web applications. 🌐

MERN stands for:
✔️ M → MongoDB
✔️ E → Express.js
✔️ R → React.js
✔️ N → Node.js

If your goal is to become a Full Stack Web Developer, this roadmap can guide you from beginner to advanced level. 💯

🧠 STEP 1: Learn Web Development Basics
Before learning MERN, understand how websites work.

📚 Learn:
✔️ How the Internet Works
✔️ HTTP & HTTPS
✔️ Frontend vs Backend
✔️ Browser & Servers
✔️ APIs Basics

🌐 STEP 2: Master HTML, CSS & JavaScript
These are the foundation of web development.

🏗 HTML
Used to create website structure.

Learn:
✔️ Headings
✔️ Forms
✔️ Tables
✔️ Semantic Tags
✔️ Audio & Video

🎨 CSS
Used for styling websites.

Learn:
✔️ Colors & Fonts
✔️ Flexbox
✔️ Grid
✔️ Responsive Design
✔️ Animations

⚡️ JavaScript
Makes websites interactive.

Learn:
✔️ Variables
✔️ Functions
✔️ Arrays & Objects
✔️ Loops & Conditions
✔️ DOM Manipulation
✔️ ES6 Concepts
✔️ Async/Await
✔️ Fetch API

🛠 STEP 3: Learn Git & GitHub
Version control is very important for developers.

Learn:
✔️ Git Basics
✔️ Push & Pull
✔️ Branching
✔️ Merge
✔️ Open Source Contribution

⚛️ STEP 4: Learn React.js
React is the frontend library used in MERN.

📚 Core Concepts:
✔️ Components
✔️ Props
✔️ State
✔️ Events
✔️ Conditional Rendering
✔️ Lists & Keys
✔️ Forms Handling

⚡️ Advanced React:
✔️ Hooks
✔️ useEffect
✔️ useContext
✔️ React Router
✔️ API Integration
✔️ Redux Toolkit
✔️ Performance Optimization

🎨 STEP 5: Learn Tailwind CSS
Modern frontend styling framework.

Learn:
✔️ Utility Classes
✔️ Responsive Design
✔️ Flex/Grid
✔️ Dark Mode
✔️ Components Styling

🟢 STEP 6: Learn Node.js
Node.js allows JavaScript to run on servers.

Learn:
✔️ Modules
✔️ File System
✔️ Event Loop
✔️ NPM
✔️ Package Management
✔️ Environment Variables

🚀 STEP 7: Learn Express.js
Express helps build backend APIs easily.

Learn:
✔️ Routes
✔️ Middleware
✔️ REST APIs
✔️ Request & Response
✔️ Error Handling
✔️ Authentication

🍃 STEP 8: Learn MongoDB
MongoDB is a NoSQL database.

Learn:
✔️ Collections & Documents
✔️ CRUD Operations
✔️ Schema Design
✔️ Mongoose
✔️ Relationships
✔️ Aggregation

🔐 STEP 9: Authentication & Security
Very important for real-world projects.

Learn:
✔️ JWT Authentication
✔️ Cookies & Sessions
✔️ Password Hashing
✔️ Role-Based Access
✔️ API Security

☁️ STEP 10: Deployment
Learn how to make your app live.

Platforms:
✔️ Vercel
✔️ Render
✔️ Netlify

🛠 Important Tools to Learn
✔️ VS Code
✔️ Postman
✔️ GitHub
✔️ MongoDB Compass
✔️ Chrome DevTools

🔥 Best Projects for MERN Stack

🟢 Beginner Projects
✔️ Todo App
✔️ Weather App
✔️ Notes App
✔️ Calculator
✔️ Quiz App

🟡 Intermediate Projects
✔️ Blog Website
✔️ Expense Tracker
✔️ Chat Application
✔️ Movie App
✔️ Portfolio Website

🔴 Advanced Projects
✔️ E-commerce Website
✔️ Social Media App
✔️ AI Chatbot
✔️ Video Streaming Platform
✔️ Learning Management System

📚 Best Resources to Learn MERN

🎥 YouTube Channels
✔️ CodeWithHarry
✔️ freeCodeCamp
✔️ Traversy Media

🚀 Suggested Learning Order
1️⃣ HTML
2️⃣ CSS
3️⃣ JavaScript
4️⃣ Git & GitHub
5️⃣ React.js
6️⃣ Tailwind CSS
7️⃣ Node.js
8️⃣ Express.js
9️⃣ MongoDB
🔟 Deployment

💡 Advice for Beginners
Don’t just watch tutorials
Build projects alongside learning

Don’t memorize code
Understand logic and flow

Don’t skip JavaScript basics
Strong JavaScript = Strong MERN Developer

@CodingCoursePro
Shared with Love

💬 Tap ❤️ if this helped you!
Please open Telegram to view this post
VIEW IN TELEGRAM
5
💻 Responsive HTML Video

Using the orientation media query in HTML video content for users devices orientation, enhancing usability and performance.
Please open Telegram to view this post
VIEW IN TELEGRAM
Please open Telegram to view this post
VIEW IN TELEGRAM
🙏2
📈PREPAID ADVERTISEMENT AVAILABLE.

Transparent - Authentic - Effective

💭Contact for deal @StarkService
Please open Telegram to view this post
VIEW IN TELEGRAM
🙏2
⌨️ CSS tip: easy layout

This layout is ideal for creating documentation pages or any website with a fixed-width sidebar for navigation and a flexible content area for displaying information.
Please open Telegram to view this post
VIEW IN TELEGRAM
🧠 15. What are Void Elements?
Void elements do not require closing tags.

Examples:
- <br>
- <hr>
- <img>
- <input>

🧠 16. What is the Purpose of alt Attribute?
alt provides alternative text for images.

Example:
<img src="cat.jpg" alt="Cute Cat">

Benefits:
Accessibility
SEO
Backup text if image fails

🧠 17. Explain Audio and Video Tags
HTML5 provides multimedia support.

Audio Example:
<audio controls>
<source src="song.mp3">
</audio>

Video Example:
<video controls width="400">
<source src="movie.mp4">
</video>

🧠 18. What is Accessibility in HTML?
Accessibility means making websites usable for everyone.

Best Practices:
- Semantic HTML
- Alt text
- Proper headings
- Keyboard support

🧠 19. What are ARIA Attributes?
ARIA improves accessibility for screen readers.

Example:
<button aria-label="Search">

Common ARIA Attributes:
- aria-label
- aria-hidden
- aria-expanded

🧠 20. Difference Between <strong> and <b>
<strong> : Semantic importance
<b> : Only bold styling

<strong> : Used for important text
<b> : Used for design

Example:
<strong>Important</strong>

<b>Bold Text</b>

Double Tap ❤️ For Part-2
2
🚀 Web Development Interview Questions with Answers — Part 1: HTML

🧠 1. What is HTML?
HTML stands for HyperText Markup Language.
It is the standard language used to create and structure web pages.

HTML is used to:
• Create headings
• Add paragraphs
• Insert images
• Create links
• Build forms
• Structure web content

Example:

<!DOCTYPE html>
<html>
<head>
<title>My Website</title>
</head>
<body>
<h1>Hello World</h1>
</body>
</html>


🧠 2. Difference Between HTML4 and HTML5
HTML4 : Older version
HTML5 : Latest version

HTML4 : No semantic tags
HTML5 : Semantic tags added

HTML4 : No direct multimedia support
HTML5 : Supports audio/video

HTML4 : Less mobile friendly
HTML5 : Mobile optimized

HTML5 Features:
<video>
<audio>
<canvas>
• Local Storage
• Semantic Tags

🧠 3. What are Semantic Tags in HTML5?
Semantic tags describe the meaning of content clearly.

Common Semantic Tags:
<header>
<nav>
<section>
<article>
<footer>

Benefits:
Better SEO
Better readability
Accessibility improvement

Example:

<article>
<h2>Blog Title</h2>
<p>Content here...</p>
</article>


🧠 4. Difference Between <div> and <span>
<div> : Block element
<span> : Inline element

<div> : Takes full width
<span> : Takes required width

<div> : Used for sections
<span> : Used for small styling

Example:

<div>Hello</div>
<span>Hello</span>


🧠 5. What is the Purpose of DOCTYPE?
<!DOCTYPE html> tells the browser which HTML version is being used.

Example:

<!DOCTYPE html>


Benefits:
Proper rendering
Avoids browser compatibility issues

🧠 6. What are Meta Tags?
Meta tags provide information about the webpage.

Example:

<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="HTML Tutorial">


Uses:
• SEO
• Responsive design
• Character encoding

🧠 7. Difference Between ID and Class
ID : Unique
Class : Reusable

ID : Uses # in CSS
Class : Uses . in CSS

Example:

<div id="header"></div>
<div class="card"></div>
<div class="card"></div>


🧠 8. What are Inline and Block Elements?
Block Elements
Start on new line
Take full width

Examples:
<div>
<p>
<h1>

Inline Elements
Do not start on new line
Take only required space

Examples:
<span>
<a>
<img>

🧠 9. Explain Forms in HTML
Forms collect user input.

Example:

<form>
<input type="text" placeholder="Enter Name">
<input type="email" placeholder="Enter Email">
<button>Submit</button>
</form>


Common Form Elements:
• input
• textarea
• select
• checkbox
• radio button

🧠 10. Difference Between GET and POST
GET : Data visible in URL
POST : Data hidden

GET : Less secure
POST : More secure

GET : Used for fetching
POST : Used for sending

Example:

<form method="GET"></form>
<form method="POST"></form>


🧠 11. What is localStorage and sessionStorage?
Both store data in browser.

localStorage : Permanent
sessionStorage : Temporary

localStorage : Remains after closing browser
sessionStorage : Removed after tab closes

Example:

localStorage.setItem("name", "Deepak");
sessionStorage.setItem("theme", "dark");


🧠 12. What are Data Attributes?
Custom attributes used to store extra information.

Example:

<div data-userid="101">User</div>


Access in JavaScript:

element.dataset.userid


🧠 13. What is iframe?
iframe embeds another webpage inside a webpage.

Example:

<iframe src="https://example.com"></iframe>


Uses:
• YouTube videos
• Google Maps
• External websites

🧠 14. Difference Between Cookies and localStorage
Cookies : Small storage
localStorage : Large storage

Cookies : Sent to server

localStorage : Not sent automatically

Example: 
document.cookie = "username=Deepak";
🚀 Web Development Interview Questions with Answers — Part 2: CSS

🧠 21. What is CSS?
CSS stands for Cascading Style Sheets.
It is used to style and design HTML elements.

CSS helps to:
• Add colors
• Set fonts
• Create layouts
• Add animations
• Make websites responsive

Example:

h1 {
color: blue;
font-size: 40px;
}


🧠 22. Difference Between Inline, Internal, and External CSS
Type : Description
Inline CSS : Written inside HTML element
Internal CSS : Written inside <style> tag
External CSS : Written in separate .css file

Inline CSS:

<h1 style="color:red;">Hello</h1>


Internal CSS:

<style>
h1 {
color: blue;
}
</style>


External CSS:

<link rel="stylesheet" href="style.css">


🧠 23. What is Specificity in CSS?
Specificity determines which CSS rule is applied when multiple rules target the same element.

Priority Order:
1. Inline CSS
2. ID Selector
3. Class Selector
4. Element Selector

Example:

#title {
color: red;
}

.heading {
color: blue;
}


ID selector has higher priority.

🧠 24. Explain CSS Box Model
Every HTML element is treated as a box.

The box model contains:
• Content
• Padding
• Border
• Margin

Structure:

Margin
└ Border
└ Padding
└ Content


Example:

div {
padding: 20px;
border: 2px solid black;
margin: 10px;
}


🧠 25. Difference Between Margin and Padding
Margin : Space outside border
Creates gap between elements

Padding : Space inside border
Creates inner spacing

Example:

div {
margin: 20px;
padding: 20px;
}


🧠 26. What is Flexbox?
Flexbox is a one-dimensional layout system used for alignment and spacing.

Benefits:
Easy alignment
Responsive layouts
Flexible spacing

Example:

.container {
display: flex;
justify-content: center;
align-items: center;
}


🧠 27. What is CSS Grid?
CSS Grid is a two-dimensional layout system.

It handles:
• Rows
• Columns

Example:

.container {
display: grid;
grid-template-columns: 1fr 1fr;
}


🧠 28. Difference Between Relative, Absolute, Fixed, and Sticky Positioning
Position : Description
relative : Positioned relative to itself
absolute : Positioned relative to parent
fixed : Fixed on screen
sticky : Sticks during scrolling

Example:

div {
position: absolute;
top: 20px;
}


🧠 29. What is z-index?
z-index controls stack order of elements.

Higher z-index appears on top.

Example:

.box {
z-index: 10;
}


🧠 30. Difference Between em, rem, %, px, vh, and vw
Unit : Meaning
px : Fixed pixels
% : Relative percentage
em : Relative to parent
rem : Relative to root
vh : Viewport height
vw : Viewport width

Example:

h1 {
font-size: 2rem;
}


🧠 31. What are Pseudo-Classes?
Pseudo-classes define special states of elements.

Examples:

a:hover {
color: red;
}


Common Pseudo-Classes:
• :hover
• :focus
• :first-child
• :last-child

🧠 32. What are Pseudo-Elements?
Pseudo-elements style specific parts of elements.

Example:

p::first-letter {
font-size: 40px;
}


Common Pseudo-Elements:
• ::before
• ::after
• ::first-letter

🧠 33. Difference Between visibility:hidden and display:none
visibility:hidden : Element hidden but space remains
display:none : Element removed completely

Example:

.box {
display: none;
}


🧠 34. What is Media Query?
Media queries make websites responsive.

Example:

@media (max-width: 768px) {
body {
background: lightblue;
}
}


🧠 35. Explain Responsive Design
Responsive design ensures websites work on:
• Mobile
• Tablet
• Desktop

Techniques:
Media Queries
Flexible layouts
Responsive images 

🧠 36. What is Mobile-First Design? 
Mobile-first design means designing for smaller screens first and then scaling upward. 

Benefits: 
Better performance 
Better UX on mobile devices