American football is a sport played between two teams of eleven (11) players with the objective of scoring points by advancing the ball into the opposing team’s end zone either by running with it or throwing it to a teammate. Therefore, points can be scored by carrying the ball over the opponent’s goal line, catching a pass thrown over that goal line, kicking the ball through the opponent’s goal posts or tackling an opposing ball carrier in his own end zone.
Once the ball crosses the plane of the goal line while it is in a player’s possession, it is scored a touchdown. A touchdown is worth six (6) points.
The team scoring a touchdown is given the bonus of trying to add one (1) or two (2) more points. These are called extra point conversion attempts.
If a team elects to go for two (2) extra points, they will line up at the two-yard line and make one attempt at either running or passing the ball into the end zone once again. If they make it, they are awarded two (2) points. If they don’t, they get no extra points.
They can also elect to go for just one (1) extra point by kicking the ball through the goal posts while snapping it from the two-yard line.
Another way for a team to score is by kicking a field goal. When a team finds themselves in a fourth-down situation, many times they will attempt to kick a field goal if they feel they are close enough for their kicker to kick the football between the upright bars of the goal post in the opponent’s end zone. A field goal is worth three (3) points.
The defense can also score two (2) points by tackling an opponent possessing the ball in his own end zone. This is called a safety! If a defensive player, intercepts a ball thrown to a receiver or recovers a fumble and manages to cross the opponent goal line with the ball in his possession, the team is awarded with a touchdown and will have the opportunity to choose how many extra point they want to go for as well.
Touchdown = six (6) points
Extra Point Conversion = one (1) point
Two-Point Conversion = two (2) points
Field Goal = three (3) points
Safety= two (2) points
In order to move the ball at least ten (10) yards forwards from the spot of the ball and score a touchdown, the offense has four (4) attempts, called downs. If a team fails to move the ball at least ten (10) yards forwards after the four (4) downs, the team loses the possession of the ball and it is the opponent team’s turn to try to move the ball at least ten (10) yards forwards in four (4) downs. Usually, if a team is too far away from the upright bars to try field goal on their fourth down, the team will choose to punt the ball the farthest away from their own end zone. If the offense manages to complete at least ten (10) yards in four (4) downs, the team is granted another four downs to move the ball forwards. If the defense can not stop the offense and the offense enter the end zone with the ball, the offense scores a touchdown.
For further and thorough explanation of the rules the NCAA offers an updated free PFD of the rulebook:
NCAA – RULEBOOK – AMERICAN FOOTBALL