Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares along the first rank toward a rook (which is on the player's first rank[note 2]) and then placing the rook on the last square that the king has just crossed. Castling is permissible under the following conditions:[5]
Neither the king nor the rook have previously moved during the game.
There cannot be any pieces between the king and the rook.
The king cannot be in check, nor can the king pass through squares that are under attack by enemy pieces, or move to a square where it would result in a check. Note that castling is permissible if the rook is attacked, or if the rook crosses a square that is attacked.
When a pawn advances two squares from its starting position and there is an opponent's pawn on an adjacent file next to its destination square, then the opponent's pawn can capture it en passant (in passing), and move to the square the pawn passed over. This can only be done on the very next move, otherwise the right to do so is forfeit. For example, if the black pawn has just advanced two squares from g7 (initial starting position) to g5, then the white pawn on f5 may take it via en passant on g6 (but only on White's next move).
When a pawn advances to the eighth rank, as a part of the move it is promoted and must be exchanged for the player's choice of queen, rook, bishop, or knight of the same color. Usually, the pawn is chosen to be promoted to a queen, but in some cases another piece is chosen; this is called underpromotion. In the diagram on the right, the pawn on c7 can be advanced to the eighth rank and be promoted to an allowed piece. There is no restriction placed on the piece that is chosen on promotion, so it is possible to have more pieces of the same type than at the start of the game (for example, two queens).
When a king is under immediate attack by one or two of the opponent's pieces, it is said to be in check. A response to a check is a legal move if it results in a position where the king is no longer under direct attack (that is, not in check). This can involve capturing the checking piece; interposing a piece between the checking piece and the king (which is possible only if the attacking piece is a queen, rook, or bishop and there is a square between it and the king); or moving the king to a square where it is not under attack. Castling is not a permissible response to a 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 legal way to remove it from attack. It is illegal for a player to make a move that would put or leave the player's own king in check.
In casual games it is common to announce "check" when putting the opponent's king in check, but this is not required by the rules of the game, and is not usually done in tournaments.
White is in checkmate, being unable to escape attack by the black bishops.
Games can be won in the following ways:
Checkmate: The player whose turn it is to move is in check and has no legal move to escape check.
Resignation: Either player may resign, conceding the game to the opponent.[6] It is usually considered poor etiquette to play on in a truly hopeless position, and for this reason high-level games rarely end in checkmate.
Win on time: In games with a time control, a player wins if the opponent runs out of time, even if the opponent has a much superior position, as long as the player still has a theoretical possibility to checkmate the opponent.
Forfeit: A player who cheats, or violates the rules of the game, or violates the rules specified for the particular tournament can be forfeited. In high-level tournaments, players have been forfeited for such things as arriving late for the game (even by a matter of seconds), receiving a call or text on a cell phone, refusing to undergo a drug test, refusing to undergo a body search for electronic devices, and unsporting behavior (such as refusing to shake the opponent's hand).
Draw by agreement: Draws are most commonly reached by mutual agreement between the players. The correct procedure is to verbally offer the draw, make a move, then start the opponent's clock. Traditionally, players have been allowed to agree to a draw at any point in the game, occasionally even without playing a move; in recent years efforts have been made to discourage short draws, for example by forbidding draw offers before move thirty.
Stalemate: The player whose turn it is to move has no legal move and is not in check.
Threefold repetition of position: This most commonly occurs when neither side is able to avoid repeating moves without incurring a disadvantage. In this situation, either player can claim a draw; this requires the players to keep a valid written record of the game so that the claim can be verified by the arbiter if challenged. The three occurrences of the position need not occur on consecutive moves for a claim to be valid. FIDE rules make no mention of perpetual check; this is merely a specific type of draw by threefold repetition.
Fifty-move rule: If during the previous 50 moves no pawn has been moved and no capture has been made, either player can claim a draw. There are several known endgames where it is possible to force a mate but it requires more than 50 moves before a pawn move or capture is made; examples include some endgames with two knights against a pawn and some pawnless endgames such as queen against two bishops. Historically, FIDE has sometimes revised the 50-move rule to make exceptions for these endgames, but at present (as of 2017) no exceptions are made. Some correspondence chess organizations do not enforce the fifty-move rule.[note 3]
Fivefold repetition of position: Similar to the threefold-repetition rule, but in this case neither player needs to claim the draw; thus a tournament director can intervene and declare the game to be drawn. This is a relatively recent (2014) addition to the FIDE rules.
Seventy-five-move rule: Similar to the fifty-move rule; however, if the final move in the sequence resulted in checkmate, this takes precedence. As with the fivefold-repetition rule, this applies independently of claims by the players, and allows a tournament director to intervene. This rule likewise is a recent addition to the FIDE rules.
Insufficient material: If neither player has a theoretical possibility to checkmate the opponent; for example, if a player has only the king and a knight left, and the opponent has only the king left, checkmate is impossible and the game is drawn by this rule. On the other hand, if both players have a king and a knight left, there is a highly unlikely yet theoretical possibility of checkmate, so this rule does not apply.
Draw on time: In games with a time control, the game is drawn if a player is out of time and the opponent has no theoretical possibility to checkmate the player.
The following information was obtained from www.wikipedia.com:
Castling
Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares along the first rank toward a rook (which is on the player's first rank[note 2]) and then placing the rook on the last square that the king has just crossed. Castling is permissible under the following conditions:[5]
En passant
When a pawn advances two squares from its starting position and there is an opponent's pawn on an adjacent file next to its destination square, then the opponent's pawn can capture it en passant (in passing), and move to the square the pawn passed over. This can only be done on the very next move, otherwise the right to do so is forfeit. For example, if the black pawn has just advanced two squares from g7 (initial starting position) to g5, then the white pawn on f5 may take it via en passant on g6 (but only on White's next move).
Promotion
When a pawn advances to the eighth rank, as a part of the move it is promoted and must be exchanged for the player's choice of queen, rook, bishop, or knight of the same color. Usually, the pawn is chosen to be promoted to a queen, but in some cases another piece is chosen; this is called underpromotion. In the diagram on the right, the pawn on c7 can be advanced to the eighth rank and be promoted to an allowed piece. There is no restriction placed on the piece that is chosen on promotion, so it is possible to have more pieces of the same type than at the start of the game (for example, two queens).
Check
When a king is under immediate attack by one or two of the opponent's pieces, it is said to be in check. A response to a check is a legal move if it results in a position where the king is no longer under direct attack (that is, not in check). This can involve capturing the checking piece; interposing a piece between the checking piece and the king (which is possible only if the attacking piece is a queen, rook, or bishop and there is a square between it and the king); or moving the king to a square where it is not under attack. Castling is not a permissible response to a 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 legal way to remove it from attack. It is illegal for a player to make a move that would put or leave the player's own king in check.
In casual games it is common to announce "check" when putting the opponent's king in check, but this is not required by the rules of the game, and is not usually done in tournaments.
End of the game
Win
Games can be won in the following ways:
Draw
There are several ways games can end in a draw: