American football is a complicated team sport which almost defies a brief and straightforward definition. There are, however, some essential rules and playing strategies which should provide a basic understanding of the game many people only see on television or in school stadiums. American football can require a substantial financial and physical commitment from players in the form of protective gear, training sessions and travel.

Essentially, American football is about advancing a leather ball over a 100 yard field in order to score a six-point touchdown, a three-point field goal, a two-point "safety," or a one-point bonus kick following a touchdown. A touchdown occurs whenever a player in possession of the football crosses a "goal line" at the 0 yard mark. Following a touchdown, the scoring team can kick a ball from the 20 yard line and earn a point for crossing between two large suspended goal posts in the end zone.

Another way a football team can score points is to attempt a long kick from the field. Since kickers have a limited kicking range, this play is generally limited to times when the team has run out of other options. The field goal kicker can make an attempt to send the ball between the upright goal posts, and if he is successful the team earns three points.

If a team fails to move the ball out of their designated end zone, the other team can earn two points for recovering the ball. This is called a "safety", and is a rare but often significant occurrence. Scoring a two point safety can give a team the advantage over the other team's one point extra point attempt. American football games can have very lopsided scores, or they could be determined by a single missed extra point kick or a safety.

American football is not just about scoring points, however. There is also a short-term objective involving the advancement of the ball. A hundred yard football field is marked off in one yard increments along the sidelines and ten yard lines visible on the field. The team in possession of the football must advance it ten yards in order to maintain possession. This is not as easy as it sounds, since the defensive team can position 11 players on their side of the ball to block the runners, intercept passes or confront the quarterback directly. A team is allowed four attempts, called downs, to advance the ball ten yards. If they are successful, the number of downs is refreshed. If they fail to advance ten yards, the other team gains possession of the ball.

American football is controlled by a clock, so teams must decide on their next plays and execute them quickly. The decision to pass the ball off to a running back or throw the ball downfield to a receiver is often made by a coach standing near the field. The defending team can also decide if the next play will involve running or passing, and they can position their players to take down a running back or block a receiver. Some plays in football are designed to gain a few yards, while others are meant to gain significant yardage or even a touchdown. A good football team will change their strategy from a short running play to a long-distance pass in order to confuse the defending team.

American football is played in 15 minute intervals called quarters. When the fourth quarter has elapsed, the game is declared over unless there is a tied score. Additional quarters may be played until a clear winner is determined. Effective use of the clock is an important element of American football, since an opposing team might only need a few seconds to set up a possible scoring drive. Each team has a designated number of time-outs to work with, which are often used to give themselves a chance to formulate and execute a last ditch scoring effort.

American football provides players with protective gear such as helmets, shoulder pads and gloves, but the play action can still be extremely dangerous. Certain techniques for bringing down other players have been deemed illegal over the years, and players are usually trained on proper tackling and contact. Football players on the field, both defensive and offensive, are either involved in blocking an opponent, taking down a runner, or intercepting a thrown pass. Excessive violence or deliberate rule violations are generally dealt with by referees, who are free to penalize any player or team for rule infractions or illegal plays.

American football may not share many similarities with the world-wide phenomenon known as soccer (futbol), but it does provide entertainment to millions of fans worldwide. American football is a popular athletic program at all different levels of educational institutions, from the Pee Wee leagues of elementary school to major public and private universities. There are a number of instructional materials available online and in bookstores which can provide a more thorough introduction to the game of American football.