Football is one of the most popular team sports in America. It is played between two teams of 11 players each. The goal is to advance the ball down the field by running or throwing it, and score points by crossing the opponent’s end zone. The game lasts for 90 minutes with a few extra minutes, called added or injury time, to allow for injuries and other stoppages in play.
The game is played on a 100-yard field with 10-yard end zones for each team. There are stripes running the width of the field at 5-yard intervals, and shorter lines, called hash marks, marking each single yard down the field. Before each play the ball is spotted on the line of scrimmage, which is where the offensive and defensive teams line up. The ball carrier, usually the quarterback, then outlines a play in a huddle with his teammates. The center then “snaps” the ball between his legs to the quarterback, who can then throw or hand off the ball. Two or more wide receivers catch the ball thrown by the quarterback, and one or more running backs carry the ball forward. Tight ends block the defense and can also catch passes.
During each play, the offensive team has four attempts – known as downs – to move the ball at least 10 yards down the field. If they fail to do so, the opposing team takes possession of the ball, often by punting on the fourth down. The offense can also choose to go for a point after touchdown or field goal, which involves running or passing the ball into the end zone from a set distance, or kicking the ball between the goal posts from anywhere on the field.
The defensive team tries to prevent the offense from scoring by tackling any player who has the ball, and intercepting any passes that are thrown. The defensive team has unlimited substitution, while the offense is limited to 11 players. A player who fumbles the ball loses possession of it for his team, while a pass that is intercepted by the opposing team’s defensive backs results in a turnover. The offensive team must also protect the quarterback by avoiding illegal contact with any defenders behind the line of scrimmage. A sack is a penalty for this, and can result in a loss of downs or even a turnover on downs. Sacks are rare, however, as the quarterback is protected by a large front line of offensive and defensive players. The quarterback is also protected by an offensive line that consists of guards and tackles. These players “snap” the ball to the quarterback and help him block the defense. Occasionally, the quarterback will be sacked by a defensive player from behind the line of scrimmage. This is a safety, and awards two points to the defense.