Just to pile on, a common trick is to sac a queen for say a minor piece, then after king takes queen, a pawn is promoted to a knight with check and a fork on the queen. After the dust settles, a player is up a minor piece.
A knight will attack different squares than a queen so promoting to a knight of course makes obvious sense in situations that warrant.
A rook or a bishop attack a subset of squares that a queen does, so why would you ever pick one of them instead of a queen? To avoid the stalemate where your opponent is not in check but has no legal moves.
