American Football Rules
The object of the game is to score points by advancing the ball to the opponent’s end zone for a touchdown, or to kick field goals, and to prevent the other team from doing likewise. The team with the most points when time has expired wins.
Game play in American football consists of a series of individual plays of short duration, outside of which the ball is dead or not in play. These can be plays from scrimmage—passes, runs, punts, and field goal attempts—or free kicks such as kickoffs. Substitutions can be made between plays, which allows for a great deal of specialization as coaches choose the players best suited for each particular situation. During a play, each team should have 11 players on the field, and each of them usually have specific tasks assigned for that specific play.
*Information and picture from Wikipedia.org. (Read more about the game rules here.)