The Super Bowl is an annual American football game that determines the champion of the National Football League (NFL). The contest is held in an American city that is chosen three to four years beforehand, usually in warm-weather or domed sites. Since 1971, the winner of the American Football Conference (AFC) Championship Game has faced the winner of the National Football Conference (NFC) Championship Game in the culmination of the NFL playoffs. Before the 1970 merger between the American Football League (AFL) and the National Football League (NFL), the two leagues met in four such contests. The first two were known as the "AFL-NFL World Championship Game." Super Bowl III in 1969 was the first such game that carried the "Super Bowl" moniker, the names "Super Bowl I" and "Super Bowl II" were retroactively applied to the first two games. The NFC/NFL leads in Super Bowl wins with 25, while the AFC/AFL has won 22. Eighteen different franchises, including teams that relocated to another city, have won the Super Bowl.