American football (known as football in the United States and gridiron in some other countries) is a sport played by two teams of eleven players on a rectangular field 120 yards long by 53.33 yards wide with goalposts at each end. The offense attempts to advance an oval ball (the football) down the field by running with or passing it. They must advance it at least ten yards in four downs to receive a new set of four downs and continue the drive; if not, they turn over the football to the opposing team. Points are scored by advancing the ball into the opposing team's end zone for a touchdown, kicking the ball through the opponent's goalposts for a field goal or by the defense tackling the ball carrier in the offense's end zone for a safety. The team with the most points at the end of a game wins.
American football evolved in the United States, originating from the sport of rugby football. The first game of American football was played on November 6, 1869 between two college teams, Rutgers and Princeton, under rules resembling rugby and soccer. A set of rule changes drawn up from 1880 onward by Walter Camp, the "Father of American Football", established the snap, eleven-player teams and the concept of downs, and later rule changes legalized the forward pass, created the neutral zone and specified the size and shape of the football.
In American football a play is a close to the ground "plan of action" or "strategy" used to move the ball down the field. A play occurs at either the snap from the center or at kickoff. Most commonly plays occur at the snap during a down. These plays vary between basic to very complicated. Football players keep a record of these plays in their playbook.
In several forms of football a forward pass is a throwing of the ball in the direction that the offensive team is trying to move, towards the defensive team's goal line. The forward pass is one of main distinguishers between gridiron football (American football and Canadian football) in which the play is legal and widespread, and rugby football (union and league) from which the North American games evolved, in which the play is illegal.
In some football codes, such as association football (soccer), the kicked forward pass is used so ubiquitously that it is not thought of as a distinct kind of play at all. In these sports, the concept of offside is used to regulate who can be in front of the play or be nearest to the goal. However, this has not always been the case. Some earlier incarnations of football allowed unlimited forward passing, while others had strict offside rules similar to rugby.