American football American football American football, referred to as football in the United States and Canada and also known as gridiron, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, which is the team controlling the oval-shaped football, attempts to advance down the field by running with or passing the ball, while the defense, which is the team without control of the ball, aims to stop the offense's advance and aims to take control of the ball for themselves. The offense must advance at least ten yards in four
American football in the United States encourage higher scoring and accommodate a smaller field of play. Some players that do not make the NFL play in indoor leagues or go to Canada and play in the Canadian Football League, which operates professionally on a somewhat older rule system with a number of differences from the American game but still recognizable as "football" to the casual American football observer. The CFL allocates half of its teams' rosters for players born and raised in Canada but allows the rest of the players to be foreign born (in practice, these spots are almost always filled by Americans); the CFL