Rules
En passant ('in passing') is the rule that surprises more beginners than any other. It's simple once you see the point behind it.
When an enemy pawn advances two squares from its starting position and lands beside one of your pawns, you may capture it as if it had only moved one square — your pawn moves diagonally to the square the enemy pawn skipped over, and the enemy pawn is removed.
Pawns were given the two-square first move to speed up the opening. En passant stops that double-step from being used to sneak past an enemy pawn that would otherwise have captured it. It keeps the original one-square logic intact.
You must capture immediately — on the very next move. If you play anything else first, you lose the right to take that pawn en passant forever. Unlike most options, this one expires after a single move.
Only with pawns, only when the enemy pawn has just made a two-square advance, and only when your pawn is on the correct rank beside it (the 5th rank for White, the 4th for Black). It's optional — you're never forced to take.
See it in a real game — play free — and you'll never be confused by it again.
When an enemy pawn advances two squares and lands beside your pawn, you may capture it as if it had moved only one square — diagonally onto the skipped square. You must do it on the very next move or lose the right.
No. En passant is optional — you may capture en passant or play any other legal move. But the right exists only for one move; if you don't take immediately, you can't take that pawn en passant later.