American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team’s end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. We do call it as Rugby in other nations.
American football is played on a field 360 by 160 feet. The longer boundary lines are sidelines, while the shorter boundary lines are end lines. Sidelines and end lines are out of bounds. Near each end of the field is a goal line; they are 100 yards (91.4 m) apart. A scoring area called an end zone extends 10 yards (9.1 m) beyond each goal line to each end line.
Each team has 11 players on the field at a time. Usually there are many more players off the field. However, teams may substitute for any or all of their players during the breaks between plays. As a result, players have very specialized roles and are divided into three separate units: the offense, the defense and the special teams.
A standard football game consists of four 15-minute quarters (12-minute quarters in high-school football and often shorter at lower levels), with a half-time intermission after the second quarter. Depending upon the level of competition, the duration of the half-time ranges from 10 to 20 minutes. At all levels, a down (play) that begins before time expires is allowed to continue until its completion, even after the clock reaches zero.