Official Tournament Rules
While variants of the game of chess exist, official tournaments comply with the rules established by the World Chess Federation, or Fédération Internationale des Échecs (FIDE). Individual countries often have their own organizations (such as the United States Chess Federation), but these organizations are commonly members of FIDE and run their tournaments in compliance with those rules. This distinction is important, as variant chess rules approach stalemates differently (some even disallow the possibility). Official tournament rules, however, have a specific stance on the subject, adhered to in official chess tournaments.
Definition
A stalemate occurs when a player can no longer make a legal move with any of his pieces. The king of the player is not currently in check, but the player is left without any moves, either because any moves would put the player’s king in check or because no legal moves are left (for example, if all remaining pawns are blocked by other pieces).
Scoring
For scored tournaments, a match ending in a stalemate is not considered a full victory or loss. Provided the move that created the stalemate was legal, the match ends as a draw immediately upon the stalemate. Each player receives half a point for the match instead of one player earning a full point for a victory and one player earning no points.
Strategy
Because a stalemate ends the match with both players gaining half a point, there is a strategic value in attempting to force a stalemate, particularly for a player on the losing end of a match. Creating a stalemate--often referred to as swindling the opponent--is seen by chess masters as a valid method of salvaging a match that would otherwise be a loss.