Dual purpose. First of all, it attacks the rook with tempo; second, it blocks the diagonal for the queen, which is now very passive.
A very strong move, supporting the d6-square, where White plans to place a rook!
Capping the d-file and the e7-bishop. If Black captures the rook, White gets a protected passed pawn and a lethal bishop on the main diagonal!
23...Bxd6?! 24.Ng5! g6 25.exd6 with a decisive advantage! Look at that bishop on b2!
Fantastic positional sacrifice by Nepo. Black will take on d4, getting a very important central pawn. Once d4 is off the board, the c5 square is available for the dark-squared bishop and the bishop pair is extremely dangerous for white. Black has another rook to use the g-file and has total domination of the dark squares.
Bishop pair and two pawns for the rook. Black is not even down material anymore!
Unity Chess Club
Jose Raul Capablanca Karel Treybal Karlsbad 1929 White to move
A classical example of space advantage from the great Capablanca. The black minor pieces are completely useless. Same story for the rooks. Black is only waiting for the end. Moreover, the pawns are fixed on light squares, which favors a possible bishop sacrifice to open the position at some point.
The most technical move! Now Black will play two rooks down and the game will be decided on the queenside.
1.axb5 gxh5 and the black rooks dream about having a life. Anyway the position is a complete disaster for Black.