Four square, also known as squareball, boxball, and in Canada, champ, is a ball game

Ball game

In American English, ball game refers specifically to either a game of basketball, baseball or American football. In British English ball game refers to any sport played with a ball....

 played among four individuals on a square court divided into quadrants. It is a popular playground game with little required equipment, almost no setup, and short rounds of play that can be ended at any time.
Four square is usually played with a rubber playground ball on a square court with four maximum players, depending on the rules (Big Four Square, Six Square, etc.).