Rules

• NFL games are 60 minutes in total, but are divided into 15-minute quarters and begin with a kickoff. Football fields measure 100 yards and the kickoff occurs at the defensive 30-yard line. A first down occurs when the offensive team gains 10 yards. The offensive team has four chances to secure these 10 yards, otherwise the other team gains possession, states the NFL Rulebook. The football is distributed throughout the team with the help of a quarterback, who can throw, hand off, or run with the ball after receiving it at the line of scrimmage.
  
  

Scoring

• There are several ways to score in football. A touchdown is worth six points and occurs when the ball is carried or caught in the end zone. Immediately after a touchdown, a chance for one more point is given through an offensive kick or for two points by running or throwing the ball into the end zone again. If the offense is unable to score a touchdown, a field goal is attempted for three points, according to the NFL Rulebook.
  
  

Offensive Positions

• The quarterback is often considered to be the most important offensive position because he leads the team and call plays and is responsible for passing the ball. The center snaps the ball to the quarterback and, along with two guards and two tackles, blocks defensive players. Two to four wide receivers may play and receive passes from the quarterback. One to two running backs can play and are responsible for taking the ball from the quarterback and running with it to the end zone. One or two tight ends can either block defensive players or catch passes.
  
  

Defensive Positions

• Defensive players try to prevent the offensive players from scoring points. The defense consists of linebackers that try to tackle the quarterback or running backs with the ball. The defensive line attempts to stop the offensive line. Cornerbacks and safeties prevent passes to the wide receivers, according to the NFL Rulebook.
  
  

Penalties

• There are several penalties in football and referees determine them, with some being more commonly called than others. A delay of game penalty occurs when the offense has not snapped the ball within 25 seconds of the play starting. Encroachment happens when defensive players move offside, whereas a false start is when the offense is offside. If an offensive or defensive player obstructs the other team's ability to catch the ball, pass interference may be called.