Football is a team sport played with two teams of 11 players on each team. In a regulation game, each team may have up to eleven players, although some variations may feature fewer players. Players are allowed unlimited substitutions during the game, but can only enter the field when the ball is dead or when play has stopped. The ball is typically passed from one player to another by the opposing team. However, players may also pass the ball from one side of the field to the other.
There are many different types of penalties in football. One such penalty is a pass interference penalty, which is a form of blocking. An unintentional pass interference penalty occurs when a player blocks or touches the intended receiver before the ball reaches him. Another offense is roughing the passer, which occurs when a defender continues to tackle a receiver after the ball is passed. Another common foul is spearing an opponent with the helmet. The penalty can result in a fine or be penalized.
Each team is allowed four downs during the game. Failure to gain yardage during the four downs will result in a turnover. Football plays are made up by the teams, and are often characterized by a team of players running all over the field. On-field plays are called by the offensive or defensive captain. In a traditional game, the quarterback of the offense calls the on-field play. The defensive captain calls the defensive play. The goal is to gain at least 10 yards and score a touchdown before the end of the game.