The most popular sport in the United States, American football is a game played by two teams of eleven players on a field. Each team has a quarterback, running backs, wide receivers, and tight ends. The offensive line, which is made up of left and right guards, and a center, is responsible for protecting the quarterback during play. They do this by blocking defenders from rushing him and also by scouting the field for open receivers to pass to during a run or passing play.
A runner may be ruled out of bounds when any part of his body, including his hands and feet, touches the ground or anything other than another player or an official on the sidelines or end lines. He is also out if he goes over the goal-line or into the end zone. Penalties can stop the clock and result in negative yards for a team, depending on the severity of the penalty. These are called by referees who throw yellow flags onto the field when they see a violation taking place.
After the ball is kicked, members of the kicking (or “receiving”) team must remain behind a line known as the line of scrimmage. During a play, the receiving team cannot cross this line until they receive a pass from the quarterback or kicker. The kicking team must also be within this line in order to attempt a field goal.
Points are scored primarily by advancing the ball into the opposing team’s end zone, either by carrying it over the goal-line or throwing it to a receiver who catches it in the end zone. Teams can also score points by kicking a field goal through the opponent’s goal-posts. The team with the most points at the end of a game wins.
Each team gets four chances – also known as “downs” – to move the ball a total of 10 yards upfield during a drive. If they fail to make it ten yards in four downs, they must turn the ball over to the defense. However, they can choose to ‘punt’ the ball downfield, thus ensuring their opponents will get a fresh set of downs closer to their own end zone.
During a play, the quarterback is protected from rushing defenders by a group of five other offensive linemen. These are the left and right tackles, the left and right guards, and the center. The center is the most important member of this group because it is his job to hike, or hand off, the ball to a running back or, if they are running a pass play, to look for open receivers to target with the pass. The quarterback may also run the ball himself.