Simplify the following text for a Grade 5 native English-speaking person.
Original: The object of the game is to checkmate the opponent 's king , whereby the king is under immediate attack ( in `` check '' ) and there is no way to remove or defend it from attack on the next move .
Simplified: The goal of the game is for each player to try and checkmate the king of the opponent . Checkmate is a threat ( ` check ' ) to the opposing king which no move can stop .