The National Football League (NFL) is a professional American football league consisting of 32 teams, divided equally between the National Football Conference (NFC) and the American Football Conference (AFC). The NFL is one of the four major professional sports leagues in North America and the highest professional level of American football in the world. The league was founded in 1920 and has since grown to become one of the most popular sports leagues in the world. The NFL's revenue comes primarily from television contracts, ticket sales, and merchandise sales. The league is also heavily involved in charitable work through its NFL Foundation.