If a pawn reaches the opponent's side of the board without any of it's fellow pieces having been taken, can the pawn then be used as any chess piece or does it have to wait for a 'senior' piece to be taken?
Pawns that reach the last row of the board promote. When a player moves a pawn to the last row of the board, he replaces the pawn by a queen, rook, knight, or bishop (of the same color). Usually, players will promote the pawn to a queen, but the other types of pieces are also allowed. (It is not required that the pawn is promoted to a piece taken. Thus, it is for instance possible that a player has at a certain moment two queens.)