What is Chess ?

Chess is a two-player board game utilizing a chessboard and sixteen pieces of six types for each player. Each type of piece moves in a distinct way. The goal of the game is to checkmate (threaten with inescapable capture) the opponent's king. Games do not necessarily end in checkmate; players often resign if they believe they will lose. A game can also end in a draw in several ways.

Besides the basic moves of the pieces, rules also govern the equipment used, time control, conduct and ethics of players, accommodations for physically challenged players, and recording of moves using chess notation. Procedures for resolving irregularities that can occur during a game are provided as well.

General Rules

Chess is played on a chessboard, a square board divided into 64 squares (eight-by-eight) of alternating color, which is similar to that used in draughts. No matter what the actual colors of the board, the lighter-colored squares are called "light" or "white", and the darker-colored squares are called "dark" or "black". Sixteen "white" and sixteen "black" pieces are placed on the board at the beginning of the game. The board is placed so that a white square is in each player's near-right corner. Horizontal rows are called ranks and vertical rows are called files. Each player controls sixteen pieces. 

At the beginning of the game, the pieces are arranged as shown in the diagram: for each side one king, one queen, two rooks, two bishops, two knights, and eight pawns. The pieces are placed, one on a square, as follows:

• The rooks are placed on the outside corners, right and left edge.
• The knights are placed immediately inside of the rooks.
• The bishops are placed immediately inside of the knights.
• The queen is placed on the central square of the same color of that of the player: white queen on the white square and black queen on the black square.
• The king takes the vacant spot next to the queen.
• The pawns are placed one square in front of all of the other pieces.

Popular mnemonics used to remember the setup are "queen on her own color" and "white on right". The latter refers to setting up the board so that the square closest to each player's right is white.

Basic moves

Each type of chess piece has its own method of movement. A piece moves to a vacant square except when capturing an opponent's piece. 

Except for any move of the knight and castling, pieces cannot jump over other pieces. A piece is captured (or taken) when an attacking enemy piece replaces it on its square (en passant is the only exception). The captured piece is thereby permanently removed from the game. The king can be put in check but cannot be captured.

• The king moves exactly one square horizontally, vertically, or diagonally. A special move with the king known as castling is allowed only once per player, per game.
• A rook moves any number of vacant squares horizontally or vertically. It also is moved when castling.
• A bishop moves any number of vacant squares diagonally.
• The queen moves any number of vacant squares horizontally, vertically, or diagonally.
• A knight moves to the nearest square not on the same rank, file, or diagonal. (This can be thought of as moving two squares horizontally then one square vertically, or moving one square horizontally then two squares vertically—i.e. in an "L" pattern.) The knight is not blocked by other pieces: it jumps to the new location.
• A pawn moves straight forward one square, if that square is vacant. If it has not yet moved, a pawn also has the option of moving two squares straight forward, provided both squares are vacant. Pawns cannot move backwards. Pawns are the only pieces that capture differently from how they move. A pawn can capture an enemy piece on either of the two squares diagonally in front of the pawn (but cannot move to those squares if they are vacant).

The pawn is also involved in the two special moves en passant and promotion.

Special moves

Castling

Castling consists of moving the king two squares towards a rook, then placing the rook on the other side of the king, adjacent to it. Castling is only permissible if all of the following conditions hold:

The king and rook involved in castling must not have previously moved;
There must be no pieces between the king and the rook;
The king may not currently be in check, nor may the king pass through or end up in a square that is under attack by an enemy piece (though the rook is permitted to be under attack and to pass over an attacked square);
The king and the rook must be on the same rank.

En passant

When a pawn advances two squares from its original square and ends the turn adjacent to a pawn of the opponent's on the same rank, it may be captured by that pawn of the opponent's, as if it had moved only one square forward. This capture is only legal on the opponent's next move immediately following the first pawn's advance. The diagrams on the right demonstrate an instance of this: if the white pawn moves from a2 to a4, the black pawn on b4 can capture it en passant, moving from b4 to a3 while the white pawn on a4 is removed from the board.

Pawn promotion

If a player advances a pawn to its eighth rank, the pawn is then promoted (converted) to a queen, rook, bishop, or knight of the same color at the choice of the player (a queen is usually chosen). The choice is not limited to previously captured pieces. Hence it is theoretically possible for a player to have up to nine queens or up to ten rooks, bishops, or knights if all of their pawns are promoted. If the desired piece is not available, the player should call the arbiter to provide the piece.

Check

A king is in check when it is under attack by at least one enemy piece. A piece unable to move because it would place its own king in check (it is pinned against its own king) may still deliver check to the opposing player.

It is illegal to make a move that places or leaves one's king in check. The possible ways to get out of check are:

• Move the king to a square where it is not in check
• Capture the checking piece (possibly with the king)
• Block the check by placing a piece between the king and the opponent's threatening piece
• If it is not possible to get out of check, the king is checkmated and the game is over

In informal games, it is customary to announce "check" when making a move that puts the opponent's king in check. However, in formal competitions check is rarely announced

End of the game