A king is in check when it is under attack by at least one enemy piece.

It is illegal to make a move that places or leaves one's king in check.

In informal games, it is customary to announce "check" when making a move that puts the opponent's king in check (in formal competitions check is rarely announced).

The possible ways to get out of check are:

1. Move the king to a square where it is not in check.

2. Capture the checking piece (possibly with the king).

3. Block the check by placing a piece between the king and the opponent's threatening piece

If it is not possible to get out of check, the king is checkmated and the game is over.