When you get a piece back where does it go in chess?

Chess pieces (King, Queen, Bishops, Knights, Rooks) can move forward, back, and from side to side, even to return to their starting position. Pawns can only more forward and can not move backwards. A pawn can only move diagonally one square to capture an opponent's chess piece. Bishops can only move diagonally along their starting square's colour. Knights can jump over pieces, but must move in an 'L' movement (two squares forward and one to either side, or one forward and two squares to either side.