Enpassant is a special pawn move in chess that many does not know. When the white pawn on 2nd rank (7th rank for black) moves 2 squares the opponent black adjacent pawn on the 4th rank can capture diagonally the white pawn that is moving 2 squares as if it had moved only one square. This applies only to pawns and the capture can be made only by the pawn that is on the players 5th rank (4th rank of the board for black and 5th rank of the board for white) you can capture only the adjacent pawn (the pawn on the very next file that may be left side or right side) that moves 2 squares and capture it only diagonally as the pawn usually captures. Enpassant is the last rule introduced to modern chess by the end of 14th century and no further changes made to the rules of chess since then.