When a player moves a piece to a position where the opponent's king is directly threatened, that king is said to be in check. The player putting the opponent's king in check must announce, "Check."
In this illustration, the white king is in check by the black queen after the black knight unblocks the queens path. This is called "discovered check." The player with a king in check must respond by escaping check. There are three ways to escape check:
• capture the checking piece
• block the checking piece
• move the king out of check
White has no piece to capture the checking queen. White can block check with knights, bishops, a rook or a queen, or White could move the king out of check to b2.