Chess

The ultimate goal of chess, achieved when a player's king is in check (under attack) and there is no legal move to escape the threat. The game ends immediately and the player delivering checkmate wins.

Short sequences of moves that exploit specific features of a position to gain a concrete advantage, such as winning material or delivering checkmate. Tactical motifs include forks, pins, skewers, discovered attacks, and double checks.

A strategic approach focused on gradually improving the placement of pieces, controlling key squares, and creating long-term structural advantages rather than seeking immediate tactical blows.

The arrangement of pawns on the board, which forms the skeleton of the position. Pawn structures determine open files, piece mobility, weaknesses, and long-term strategic plans. Because pawns cannot move backward, structural decisions are often permanent.

Foundational guidelines for the initial phase of the game, including controlling the center with pawns and pieces, developing knights and bishops to active squares, castling early for king safety, and avoiding unnecessary pawn moves.

The body of knowledge and methods used to convert advantages in the final phase of the game, when few pieces remain. Endgame technique includes king activity, passed pawn promotion, opposition, and knowledge of theoretical positions.

A system for estimating the relative strength of pieces. Conventionally, a pawn equals 1 point, a knight and bishop each equal 3, a rook equals 5, and a queen equals 9. The king has infinite value since its loss ends the game.

A special move involving the king and a rook, executed by moving the king two squares toward a rook and placing the rook on the square the king crossed. It can only be performed when neither piece has previously moved, no pieces stand between them, the king is not in check, and the king does not pass through or land on an attacked square.

A special pawn capture that can occur when a pawn advances two squares from its starting position and lands beside an enemy pawn. The enemy pawn may capture it as if it had moved only one square. This capture must be made immediately on the very next move or the right is forfeited.

A mathematical system for calculating the relative skill levels of players, developed by Arpad Elo and adopted by FIDE. A player's rating rises or falls based on game results relative to the ratings of opponents. A rating difference of 200 points corresponds to an expected score of roughly 75% for the higher-rated player.