Setup
The pieces are divided, by convention, into White and Black sets. Each player is referred to by the color of their pieces and begins the game with sixteen pieces. These comprise one king, one queen, two rooks, two bishops, two knights and eight pawns. White moves first. The colors are chosen either by a friendly agreement or by a tournament director. The players alternate moving one piece at a time (with the exception of castling, when two pieces are moved simultaneously). Pieces are moved to either an unoccupied square, or one occupied by an opponent's piece, capturing it and removing it from play. With one exception (en passant), all pieces capture opponent's pieces by moving to the square that the opponent's piece occupies.
Chess is played on a square board of eight rows (called ranks and denoted with numbers 1 to 8) and eight columns (called files and denoted with letters a to h) of squares. The colors of the sixty-four squares alternate and are referred to as "light squares" and "dark squares". The chessboard is placed with the light squares at the players' right, and the pieces are set out as shown in the diagram, with each queen on its own color.
When a king is under immediate attack by the opponent's pieces, the king is said to be in check. When in check, only moves that result in a position in which the king is not in check are permitted. Each player must not make any move that would place their king in check. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there is no way to remove the king from attack.