Chess is a two-player strategic board game that dates back over 1500 years. It's survived in its modern form for around 500 years, and chess tournaments have been held regularly around the world since the 1850's.
The game is typically played between two players on an 8x8 board with alternating colors, black and white. Each player has 16 pieces: 8 Pawns, 2 Rooks, 2 Knights, 2 Bishops, 1 Queen, and 1 King. Players alternate moves, with the player using White pieces moving first, and the player with Black pieces moving second. The goal of the game is to capture your opponent's King. An immediate threat to the King is called a check; the game is won when one player's King is in check and no move by that player can prevent capture of the King on the next turn; this situation is called checkmate. A number of situations can produce draws, such as the lack of pieces on the board to give checkmate by either side.
Games may also be played under a time constraint, where each player has a certain amount of time to make their moves, and running out of time constitutes a loss. Some systems give a fixed amount of time for the entire game for each player; others allow more time as more moves are made.
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Tag Usage This tag is for questions about the standard two-player game on an 8x8 board: historical games, strategy, openings, and endgame, among other topics. Questions about related games, like Xiangqi (Chinese chess) and Shogi (Japanese chess), should not be tagged as chess.
Diagrams Questions about a specific board position are much easier to answer with a diagram. To create a diagram, visit this site (or a similar one), set up the position you're asking about, and add the resulting image to your question.
Chess Stack Exchange Site Detailed questions of fine points of chess strategy and tactics will likely be better answered on the chess.stackexchange.com, which has a much larger community of chess enthusiasts. Nevertheless, chess questions are also on-topic here, and many beginner/recreational questions will be answered well here.