What are the basic rules of American football?

American football is played between two teams of 11 players on a 100-yard field. The offensive team has four attempts, called downs, to advance the ball at least 10 yards. If they succeed, they get a new set of four downs. If they fail, possession transfers to the other team. Points are scored by carrying or catching the ball in the opponent's end zone for a touchdown, worth 6 points, followed by a kick for an extra point or a two-point conversion. A field goal kicked through the uprights scores 3 points. The defense can score 2 points with a safety. Games consist of four 15-minute quarters, and the team with the most points wins.