What checkmate is
Mate is check with none of the three ways out. No check, no mate.
Mate is a check where none of the three ways out works: you cannot run, you cannot block and you cannot capture the attacker. The game ends on the spot. Look at the black king: the three marked squares are the only ones he could go to, and they are all on the same rank. His own pawns, which exist to protect him, are what trap him.
Deliver mate in one move.
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