In the game chess what is the special exception of taking en-passant?
En-passant happens when the opponent moves a pawn up two
squares, and only the turn immediately after the pawn moves, next
to one of your pawns. Then, you take diagonally to the unoccupied
space behind his/her pawn and remove his piece. It is the only
chess move where the capturer does not take the opponent's piece's
place.