In this game White controls three kings while Black controls three knights, that move like in chess.

Kings can capture knights, while knights can't capture kings.
Putting a king under check has no special meaning to this game.

Black wins if he's able to bring any of his knights inside the 3x3 area at the top right corner of the board, called "castle".
White wins if he's able to capture all knights, or when Black doesn't have any legal move.