Defending against mate, mix
Once you are in checkmate, the game is over and you lost. That’s why you always have to defend against a threat of checkmate.
You already know how to defend a piece. Defending the king works the same way:
Moving away: your king walks away from the threat.
Blocking: you put another piece between the attacker that threatens mate and the king.
Capturing: you take the attacking piece.
Protecting: you guard the square that the attacker needs to occupy in order to mate the king.
Sometimes the only way to prevent checkmate is by giving up material. Have a look at the example. White has to give up a rook (sacrifice). You rather lose a piece than lose the game!
What do you have to do?
Defend against checkmate.