Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. Each player begins the game with sixteen pieces: One king, one queen, two rooks, two knights, two bishops, and eight pawns. Pieces move in different assigned ways according to their type, and accordingly are used to attack and capture the opponent's pieces. The object of the game is to checkmate the opponent's king, whereby the king is under immediate attack (in "check") and there is no way to move or defend it.
Games of chess begin according to either standard (studied in-depth) or non-standard openings, in which the purpose is the development of pieces —moving them into positions where they can be effective. Moves are chosen with offensive and defensive considerations, according to a strategy of attack, or to respond to urgent threats. Throughout the game, players seek to set up and execute exchanges of pieces which gain the advantage in terms of piece value or board position (for example, one may exchange a knight for a knight plus a pawn). At critical stages, winning often requires solving unique or clever situations or puzzles. In addition to checkmate, games may be won by resignation, if too much material has been lost, or if one's position is severely compromised and a checkmate appears unavoidable. Strong players are those who have studied game openings and have developed the skills of depth and insight in their reading of the game position. Theoreticians have developed extensive chess strategies and tactics since the game's inception.
The game's present form emerged in Europe during the second half of the 15th century, an evolution of an older Indian game, Shatranj (cf. Chaturanga). Organized competitive chess began during the 16th century. The first official World Chess Champion, Wilhelm Steinitz, claimed his title in 1886; the current World Champion is Viswanathan Anand from India. In addition to the World Championship, there is the Women's World Championship, the Junior World Championship, the World Senior Championship, the Correspondence Chess World Championship, the World Computer Chess Championship, and Blitz and Rapid World Championships (see fast chess). The Chess Olympiad is a popular competition among teams from different nations. Online chess has opened amateur and professional competition to a wide and varied group of players. Chess is a recognized sport of the International Olympic Committee, and international chess competition is sanctioned by the FIDE. Chess is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments. Some other popular forms of chess are fast chess and computer chess. There are many chess variants that have different rules, different pieces, and different boards. These variants include blindfold chess and Fischer Random Chess/Chess960.
Computers have been used for many years to create chess-playing programs, and their abilities and insights have contributed significantly to modern chess theory. One, Deep Blue, was the first machine to overcome a reigning World Chess Champion in playing ability when it defeated Garry Kasparov in 1997.