According to J.K. Rowling’s Harry Potter novels, seven players are on a Quidditch team. Each team has three Chasers, two Beaters, one Keeper, and one Seeker.
The positions have different jobs: Chasers try to score with the Quaffle, Beaters defend teammates and disrupt opponents with Bludgers, the Keeper guards the goal hoops, and the Seeker pursues the Golden Snitch. Harry becomes Gryffindor’s Seeker at Hogwarts.
The number seven describes the players on one team, not the number of balls used in the game. Quidditch uses one Quaffle, two Bludgers, and one Golden Snitch. Rowling later inspired real-world versions of the sport, although those adaptations modify rules and equipment.