Chess is one of the world's most popular board games; it is played both recreationally and competitively in clubs, tournaments, online, and by mail or e-mail (correspondence chess).
When a game begins, one player controls the sixteen white pieces while the other uses the sixteen black pieces. The colors are chosen either by a friendly agreement, by a game of chance such as pick-a-hand, or by a tournament director. The first player, referred to as White, always moves first and therefore has a slight advantage over Black. The chessboard is placed so that each player has a white square in the near right hand corner, and the pieces are set out as shown in the diagram.
Each kind of chess piece moves a different way. The rook (colloquially known as a "castle") moves any number of vacant spaces vertically or horizontally, while the bishop moves any number of vacant spaces in any direction diagonally (meaning a bishop will always remain on the same color; note that each side has a bishop for each colored square, and between them they cover the whole board. Losing one bishop often creates weaknesses on the same colored square as the lost bishop). The queen is a combination of the rook and bishop (it can move any number of spaces diagonally, horizontally, or vertically). The king can move only one square horizontally, vertically, or diagonally except when a player castles. The knight can jump over occupied squares and moves two spaces horizontally and one space vertically (or vice versa), making an L shape; a knight in the middle of the board has eight squares to which it can move. Note that every time a knight moves, it changes square color.
With the exception of the knight, pieces cannot jump over each other. One's own pieces ("friendly pieces") cannot be passed if they are in the line of movement, and a friendly piece can never replace another friendly piece. Enemy pieces cannot be passed, but they can be "captured". When a piece is captured (or taken), the attacking piece replaces the enemy piece on its square (en passant being the only exception). The king cannot be captured in regular chess, only put in check. If a player is unable to get the king out of check, checkmate results, with the loss of the game.
Pawns capture differently than they move; they can capture an enemy piece on either of the two spaces adjacent to the space in front of them (i.e., the two squares diagonally in front of them), but cannot move to these spaces if they are vacant; conversely, a pawn can move forward one square, but only if that square is unoccupied. Alternatively, a pawn can move two squares forward if it has not moved yet and both squares are empty. A pawn cannot move backward. If a pawn advances all the way to the eighth rank, it can be promoted to any other piece, except a King or another pawn — in practice, the pawn is almost always promoted to a queen.
Chess games do not have to end in checkmate — either player may resign if the situation looks hopeless. Also, games may end in a draw (tie). A draw can occur in several situations, including draw by agreement, draw by impossibility of checkmate (usually because of insufficient material to checkmate), stalemate, threefold repetition, or the fifty move rule.
Until the 1970s, at least in English-speaking countries, chess games were recorded and published using descriptive chess notation. This has been supplanted by the more compact algebraic chess notation. Several notations have emerged, based upon algebraic chess notation, for recording chess games in a format suitable for computer processing. Of these, Portable Game Notation (PGN) is the most common. Apart from recording games, there is also a notation Forsyth-Edwards Notation for recording specific positions. This is useful for adjourning a game to resume later or for conveying chess problem positions without a diagram.