In chess, a flight square is a square to which a piece can move if it is threatened. Chess is a recreational and competitive game for two players. ... // Look up square in Wiktionary, the free dictionary. ...

If the king is placed in check, it must move to a flight square on the next move (unless, of course the check can be blocked). If it has no flight square, then it is usually checkmate. Staunton chess pieces, left to right: pawn, rook, knight, bishop, queen, and king. ... In games such as chess, shogi and xiangqi, a check is an immediate threat to capture the king. ... Checkmate (frequently shortened to mate) is a situation in chess (and in other boardgames of the chaturanga family) in which one players king is under attack and there is no way to meet that threat; it is a check from which there is no escape. ...

One way to win "material" from an opponent (that is to say, end up with more pieces or more valuable pieces left on the board) is to trap a piece by removing all of its flight squares (through attacking or occupying them), then threatening to capture it.