En passant is a special chess rule that allows a pawn to capture an enemy pawn that has just moved two squares forward on an adjacent file. The capturing pawn moves to the square that the enemy pawn passed over, as if it had moved only one square. This rule prevents a pawn from using its two-square move to evade capture by an enemy pawn¹.

En passant is a French expression that means "in passing" ¹². It is one of the two special moves in chess, the other being castling ⁴. It can only be performed on the turn immediately after the enemy pawn moves two squares forward ¹². The notation for en passant is the same as any other pawn capture, except that it may be followed by "e.p." or similar ¹.

Source: Conversation with Bing, 6/13/2023 (1) En passant - Wikipedia. https://en.wikipedia.org/wiki/En_passant. (2) En Passant - Chess Terms - Chess.com. https://www.chess.com/terms/en-passant. (3) How to Understand En Passant in Chess: 5 Steps (with Pictures) - wikiHow. https://www.wikihow.com/Understand-En-Passant-in-Chess. (4) En passant – Wikipédia, a enciclopédia livre. https://pt.wikipedia.org/wiki/En_passant.