Tennis is a game played between two single players, in the singles game, or two teams of two players each, in the doubles game. To play, the players use a strung racquet to hit the tennis ball and send it over the net into the opponent's court. The purpose of the game is to send the ball fairly into the opponent's court in such a way that the opponent cannot return it fairly into your own court. This would include not being able to return it at all, causing the opponent to return it low and into the net, or returning it outside of the boundaries of your own court. The game is played all over the world, professionally and by amateurs. The simplicity of the game makes it possible for anyone who can hold a racquet, including those in wheelchairs and the very old and very young, to participate.