You play White with the full set of sixteen pieces. Black has a king, eight pawns and a knight and a bishop. Checkmate the black king to win. This is real chess with real rules, so castling, en passant and promotion all work, and a pawn that reaches the far side becomes a queen.
The knight and bishop like to work together. Keep your pieces defended and trade them off one at a time.
Three levels: on easy Black moves at random, on medium it usually grabs a piece you leave undefended, and on hard a real chess engine looks a few moves ahead. Win once for a silver star, and ten times without undo for a gold one.