Deflection is a tactic that forces an opposing piece to leave the square, rank or file it occupies, exposing the king or a valuable piece. It is typically used in the context of a combination or attack, where the deflected piece is critical to the defence.
In this position Black has moved his knight from a7 to b5 preventing either pawn from advancing.
I want to interfere with this defence... Play
Another deflection tactic that wins a queen Play