Coaches often choose one or two "captains" for their team, which designates them as both a symbolic and verbal leader on the court. In competition, only the captain is allowed to talk to the referee when disputing a play or call. The player chosen is someone who has the ability to be a liaison between the coaches, players and referee. This person must be assertive, persuasive and level-headed.
Just because a player is deemed a captain doesn't necessarily mean they're the most skilled athlete on the team; coaches normally choose a captain based on their ability to connect with and inspire their fellow teammates.