What is Multicasting?
Multicasting allows an observable to share its execution across multiple subscribers, so that all subscribers receive the same emitted data at the same time. By default, observables in RxJS are “unicast,” meaning each subscription creates a separate execution of the observable. This can lead to multiple API calls or side effects if several components subscribe to the same observable.

Multicasting ensures that only one execution occurs, regardless of how many subscribers are attached to the observable. This is particularly useful in scenarios where expensive operations (such as HTTP requests) should be shared across multiple components without being re-executed multiple times.