En Passant

French for in passing, this special pawn capturing move results from Pawns being able to advance two squares on their initial move. If an opponent's Pawn should do so, and pass the player's Pawn, then you can optionally capture your opponent's Pawn as if it had moved only one square.

Many beginner chess players are unfamiliar with the en passant rule, but understanding it is crucial for the player not to miss an opportunity for a pawn capture.