You play White with just a king and queen. Checkmate the lone black king within 50 moves to win. This game uses the real rules of chess, and the black king is moved by a real chess engine, so it will run to the safest square every time.
Two things to watch out for. Stalemate: if the black king can't move but isn't in check, the game is a draw, so always leave it a square until the final move. And don't give the queen away: if the king can capture it, king against king is a draw.
The three-fold repetition rule is ignored, so shuffling back and forth won't spoil a winning game.