American football is typically played on a field resembling the one pictured above. It consists of 100 yards (300 feet). The yard number ascends from the end zone (0 yard line) towards midfield (the 50 yard line) and it also ascends from the other end zone (0 yard line) towards midfield (the 50 yard line). In each end zone there is a goal post that rises off the ground.
The goal of American football is to outscore the opponent. There are several ways to score. Kicking the ball through a goal post in your opponent's end zone is called a field goal and is worth 3 points. Getting the ball into the end zone of an opponent by running it or passing it is called a touchdown and is worth 6 points. After each touchdown a team is allowed to choose between attempting an extra point or going for a 2 point conversion. An extra point is worth 1 point and it is accomplished by kicking the ball through the goal posts from a short distance. A 2 point conversion is worth 2 points and it is achieved by getting the ball into the end zone by running with it or catching the ball inside the end zone. The last and most uncommon way to score is called a safety and it is worth 2 points. To score a safety, one team must tackle an opposing player with the ball in that player's own end zone.
The game is typically divided up into four quarters, consisting of up to 15 minutes. The team with the highest score at the end of the game is declared the winner. In the event of a tie, there may be an overtime. The rules for overtime vary depending on the league in question.
Beginning the game
The game begins with a coin flip. The winner of the flip may choose to kick the ball, receive the ball or pick one side of the field to defend. The team that kicks the ball to begin the game usually receives the ball at the beginning of the second half of the game.
The actual game starts with a kickoff, where the kicking team must kick the ball to the opposing team. The receiving team then may catch it and run with the ball towards the end zone. The receiving team must stop running once the player carrying the ball is tackled (physically brought to the ground by an opposing player)
When the person receiving the ball on the kickoff gets tackled, his team's offense takes the field.
Continuing the game (post kickoff)
The offense has four chances to move the ball 10 yards. It is the goal of the opponent to prevent this movement. Each chance is called a down. If an offense runs out of downs, the ball is handed over to the opponent at the spot at which they were stopped. An offense that has not moved the ball 10 yards by their 4th down (attempt), typically opts to punt the ball back to the opponents. A punt is similar to the kickoff, except that on a punt the ball is kicked in midair. The reason that a team typically elects to punt it back on 4th down is so that the opponent has a longer way to go to get a touchdown.
A down begins when the man playing center snaps the ball from the line of scrimmage to the quarterback. It is then that the offense is allowed to move towards the end zone and that the defense is allowed to try to tackle the ball carrier.
Moving the ball
There are two ways for an offense to move the ball on its chances (downs). Option one is to run the ball. In this situation, the quarterback usually receives a snap from center and either hands, pitches or tosses the ball to a running back or he may decide to run with the ball himself. Option two is for the quarterback to receive the snap from the center and then attempt to throw it forward down the field towards the opponent's end zone. The player catching the ball is then allowed to run towards the end zone until he is tackled. If the offense succeeds in moving the ball further than 10 yards then they are awarded an additional four chances (downs). The ways in which the ball can be thrown or run are numerous, depending on the preference of the team and its personnel.
If one team scores through a touchdown or a field goal, they are then required to kick the ball back to the opponent. Then the opponent's team has a chance to play offense.
The ball can be turned over (surrendered to the opponent) in several different ways. The first way is when an offense runs out of chances (downs). This is called a turnover on downs. A second way is when the offense opts to punt. A third way is when a player on offense passes the ball but it is accidentally caught by a defender rather than his intended target. This is called an interception. A fourth way to turnover the ball in American football is called a fumble. This is when an offensive player drops the ball or gets it taken away from his hands and a defender picks the ball up.
Whether on offense or defense, each team puts 11 players on the field at a time. The position names vary from offense to defense. There are several different position types in American football. Depending on the play, there may be more or less of a particular position type on the field at a time.
Basic positions in American football include the following.
On offense: offensive guard, offensive tackle, center, quarterback, halfback, fullback, tight end and wide receiver. On defense: defensive tackle, defensive end, linebacker, cornerback and safety. Some of the positions are implied in their names. For example, the purpose of an offensive guard is to guard the ball carrier, a safety plays far away from the line of scrimmage and functions as the last line of defense on an American football defense. Other positions are a bit more intricate.
Each offensive player type has a set of primary duties that may involve any mixture of the following responsibilities: passing the ball, running the ball, blocking for the passer, blocking for the runner or catching the ball.
Defensive player types are more reactive. They are all about defending a particular type of offensive player. You might consider them a mirror to the offensive personnel. Thus in order to cover the offensive players called wide receivers (speedy pass catchers), defenses respond with cornerbacks (equally fast players).
A third set of personnel on an American football team is called special teams. These players are on the field when their team is kicking or receiving kicks. Positions include: kicker, kick returner, punter and punt returner.
There are many penalties in American football. Examples of penalties include: moving beyond the line of scrimmage before the play starts, delivering particularly dangerous types of hits to other players and tackling a person who is not the ball carrier.
Examples of plays
1. On 1st down with 10 yards to go the center snaps the ball to the quarterback. The quarterback hands off to the halfback who runs 3 yards before being tackled.
The result: the offense is now on 2nd down and has 7 more yards to go before receiving four new downs.
2. On 2nd down with 7 yards to go, the quarterback receives the ball from the center on a snap. He passes to a wide receiver who runs 36 yards and is tackled at midfield.
The result: the wide receiver got 36 yards on the player. Therefore, the offense receives four new downs and is closer to the end zone.
3. On 3rd down and 1, the quarterback receives a snap from the center and passes it to a tight end who runs a few yards until he is in the opponent's end zone.
The result: since an offensive player reached the end zone with the ball, the offense scores a touchdown. The offense receives 6 points and may now choose to kick an extra point or go for a 2 point conversion before they must kick the ball back to their opponent.