What you need to know about American Football: A Beginner's Guide.
One 11-man team has possession of the football. It is called the offense and it tries to advance the ball down the field, by running with the ball or throwing it, and score points by crossing the goal line and getting into an area called the end zone.
The other team (also with 11 players) is called the defence. It tries to stop the offensive team and make it give up possession of the ball. If the team with the ball does score or is forced to give up possession, the offensive and defensive teams switch roles (the offensive team goes on defence and the defensive team goes on offense), until all four quarters of the game have been played.
TIMING Games are divided into four 15 minute quarters, separated by a 12 minute break at halftime. There are also 2 minute breaks at the end of the first and third quarters as teams change ends of the field after every 15 minutes of play. Each offensive team has 40 seconds from the end of a given play until they must snap the ball for the start of the next play, otherwise they will be penalised. The clock stops at the end of incomplete passing plays, when a player goes out of bounds, or when a penalty is called. The clock starts again when the ball is re-spotted by an official.
THE PLAYERS Each team has 3 separate units: the offense, those players who are on the field when the team has possession of the ball; the defence, players who line up to stop the offense; and special teams that only come in on kicking situations (punts, field goals, and kick-offs). Only 11 players are on the field from one team at any one time.
THE KICKOFF A game starts with the kick-off. The ball is placed on a kicking tee at the defence's 30-yard line, and a special kicker kicks the ball to the offense. A kick return man from the offense will try to catch the ball and advance it by running. Where he is stopped is the point from which the offense will begin its drive, or series of offensive plays. When a kick-off is caught in the offense's own end zone, the kick returner can either run the ball out of the end zone, or kneel in the end zone to signal a touchback - a sign to stop the play. The ball is then placed on the 20-yard line, where the offense begins play.
FIRST DOWN All progress in a football game is measured in yards. The offensive team tries to get as much "yardage" as it can to try and move closer to the opponent's end zone. Each time the offense gets the ball, it has four downs, or chances, in which to gain 10 yards. If the offensive team successfully moves the ball 10 or more yards, it earns a first down, and another set of four downs. If the offense fails to gain 10 yards, it loses possession of the ball. The defence tries to prevent the offense not only from scoring, but also from gaining the 10 yards needed for a first down. If the offense reaches fourth down, it usually punts the ball (kicks it away). This forces the other team to begin its drive further down the field.
MOVING THE BALL The Run and the Pass A play begins with the snap. At the line of scrimmage (the position on the field where the play begins), the quarterback loudly calls out a play in code and the player in front of him, the centre, passes, or snaps the ball under his legs to the quarterback. From there, the quarterback can throw the ball, hand it off, or run with it.
THE TACKLE The defence prevents the offense from advancing the ball by bringing the ball carrier to the ground. A player is tackled when one or both of his knees touch the ground. The play is then over. A play also ends when a player runs out of bounds.
SCORING There are four ways to score points in football.
TOUCHDOWN = 6 POINTS A touchdown is the biggest single score in a football game. It is worth six points, and it allows the scoring team an opportunity to attempt to get an extra point. To score a touchdown, the ball must be carried across the goal line into the end zone, caught in the end zone, or a fumble recovered in the end zone, or an untouched kick-off recovered in the end zone by the kicking team.
EXTRA POINT and the TWO-POINT CONVERSION = 1 or 2 POINTS Immediately following a touchdown, the ball is placed at the opponent's two-yard line, where the offense has two options. Usually the offense will kick an extra point, also called the point after touchdown, conversion, or PAT. If the offense successfully kicks the ball through the goal posts, it earns one point. The offense can also score two points by running or throwing the ball into the end zone in the same manner as you would score a touchdown.
FIELD GOAL = 3 POINTS If the offense cannot score a touchdown, it may try to kick a field goal. Field goals are worth three points and often are the deciding plays in the last seconds of close games. They can be attempted from anywhere on the field on any down, but generally are kicked from inside the defence's 45-yard line on fourth down. For a field goal to be "good", the field goal kicker must kick the ball through the goal-post and over the crossbar.
SAFETY = 2 POINTS The safety is worth two points. A safety occurs when the offensive ball carrier is tackled behind his own goal line.
TURNOVERS While trying to advance the football to the end zone, the offense may accidentally turn the ball over to the defence in one of two ways:
THE FUMBLE When the ball carrier or passer drops the ball, that's a fumble. Any player on the field can recover the ball by diving on it or he can run with it. The team that recovers a fumble retains possession of the ball.
THE INTERCEPTION An aggressive defence can regain possession of the ball by catching (intercepting) passes meant for players on the other team. Both fumble recoveries and interceptions can be run back into the end zone for touchdowns.