DEFENSE. There are three basic levels to a defensive formation: the line, linebackers and the secondary. Variations to defensive formations come in the number and combinations of players at each of these levels. Traditionally, defensive formations are named according to the number of down linemen and linebackers.

Defensive players only play on offense every once in a while. There are players who specialize in playing in certain situations, like when a team is on defense and knows it’s opponent is going to throw the ball. Then there are the most specialized of all players, the kickers. Kickers are a group apart.

Once a forward pass is in the air it is a loose ball and thus any eligible receiver – all defensive players are eligible receivers – may try to catch it. When a defensive player catches a forward pass it is an interception and their team gains possession of the ball.

Penalty: For Roughing the Passer: Loss of 15 yards and an automatic first down; disqualification if flagrant. When in doubt about a roughness call or potentially dangerous tactic against the quarterback, the Referee should always call roughing the passer.

Both college and the NFL also have offensive pass interference rules. At both levels, the offense can’t block the defense beyond the line of scrimmage while the ball’s in the air. Receivers aren’t allowed to push off defenders.

Punt: A kick made when a player drops the ball and kicks it while it falls toward his foot. A punt is usually made on a fourth down when the offense must surrender possession of the ball to the defense because it couldn’t advance 10 yards.

The umpire is required to yell “Infield fly, if fair” and will typically raise one arm straight up to signal to everyone that the rule is in effect. If the umpire believes the catch is a sure thing, he can call the play as an infield fly and declare the batter out, even if the ball was not caught.