In tennis, a Ball Boy or Ball Girl is a young person who retrieves balls that go out of play.
They also supply new balls to the players before serving. Ball boys and girls are usually positioned at the back and sides of the court.
The back positions give balls to the serving player. The net positions collect balls from the court and roll them to the back. Ball kids help keep the match flowing smoothly.
Former world No. 1 Roger Federer started as a ball boy at the Swiss Indoors in 1993. Other top players who have been ball kids include Billie Jean King. There are plenty more other players who served as ball boys or ball girls.