The FIDE Laws of Chess
RULES OF PLAY
1: The nature and objectives
1.1 The game of chess is played between two opponents who move their pieces alternately on a square board called a 'chessboard'. The player with the white pieces commences the game. A player is said to 'have the move', when his opponent's move has been made.
1.2 The objective of each player is to place the opponent's king 'under attack' in such a way that the opponent has no legal move which would avoid the 'capture' of the king on the following move. The player who achieves this goal is said to have 'checkmated' the opponent's king and to have won the game. The opponent whose king has been checkmated has lost the game.
1.3 If the position is such that neither player can possibly checkmate, the game is drawn.