The National Football League (NFL) is a professional American football league that constitutes one of the four major professional sports leagues in North America. It is composed of 32 teams divided equally between the National Football Conference (NFC) and the American Football Conference (AFC). The highest professional level of the sport in the world, the NFL runs a 17-week regular season from the week after Labor Day to the week after Christmas, with each team playing sixteen games and having one bye week each season.
Out of the league's 32 teams, six (four division winners and two wild-card teams) from each conference compete in the NFL playoffs, a single-elimination tournament culminating in the Super Bowl, played between the champions of the NFC and AFC. The champions of the Super Bowl are awarded the Vince Lombardi Trophy. Various other awards exist to recognize individual players and coaches. Most games are played on Sunday afternoons; some games are also played on Mondays and Thursdays during the regular season. There are games on Saturdays during the first two playoff weekends. Sometimes, there are also Saturday games during the last few weeks of the regular season. The NFL was formed on August 20, 1920, as the American Professional Football Conference; the league changed its name to the American Professional Football Association (APFA) on September 17, 1920, and changed its name to the National Football League on June 24, 1922, after spending the 1920 and 1921 seasons as the APFA. In 1966, the NFL agreed to merge with the rival American Football League (AFL), effective 1970; the first Super Bowl was held at the end of that same season in January 1967. Today, the NFL has the highest average attendance (67,591) of any professional sports league in the world and is the most popular sports league in the United States. The Super Bowl is among the biggest club sporting events in the world and individual Super Bowl games account for many of the most-watched television programs in American history. At the corporate level, the NFL is a nonprofit 501(c)(6) association. The NFL's executive officer is the commissioner, who has broad authority in governing the league. Each team is allowed to have up to 53 players during the regular season, but only 46 can be active (eligible to play) on game days. Teams are given exclusive rights to sign free agents that have three or fewer seasons in the league, but free agents that have been in the league at least four years can sign with any team of their choosing. Each team is subject to a salary cap. The champions of the most recent season, the 2013 season, are the Seattle Seahawks, who defeated the Denver Broncos by a score of 43-8 in Super Bowl XLVIII. The team with the most championships is the Green Bay Packers, who have won 13 championships. The team that currently has the most Super Bowl championships is the Pittsburgh Steelers, who have won six.