Different forms of competition can be called a championship. It is usually the final competition in a tournament (a series of competitions). For example, the FIFA World Cup is a tournament held every four years. The winner of the final competition of each tournament becomes that tournament's champion. In a league system, the championship is the final competition of a regular season. In some league systems, a series of playoffs is used to determine the champion of a season. There is one champion for each season.
Championship Facts for Kids. Kiddle Encyclopedia.