Boxing is a martial art and combat sport in which two people throw punches at each other, usually with gloved hands. Historically, the goals have been to weaken and knock down the opponent. Amateur boxing is both an Olympic and Commonwealth sport and is a common fixture in most international games—it also has its own World Championships. Boxing is supervised by a referee over a series of one- to three-minute intervals called rounds. The result is decided when an opponent is deemed incapable to continue by a referee, is disqualified for breaking a rule, resigns by throwing in a towel, or is pronounced the winner or loser based on the judges' scorecards at the end of the contest.