"Hi, good summer? Listen, I've been made Gryffindor Quidditch Captain."
-- Angelina Johnson (OP12)
The Captain of a Quidditch team is the member tasked with being its leader. Captains fulfil many of the duties, such as coming up with strategies, coaching other players, and managing practice schedules, that might be done by a coach in another sport. A player from any position can be the captain.
The captain of a Hogwarts Quidditch teams is not always the most senior player on the team (HBP9).
If one is needed, a new captain is chosen by Hogwarts staff before the school year starts. Harry received his Team Captain’s badge with the owl bringing his list of books before the start of his sixth year (HBP6).
Professional teams, where there are managers or coaches for the organisational and training side, would expect the team captain to lead by example and speak on behalf of the players.
Lexicon list of Quidditch players