In football players use their bodies to move a ball that has a bladder inside. This bladder is made of a synthetic material that gives the ball its unique elongated shape. The inflated ball is covered in a leather covering to protect it. A valve protrudes through the leather to allow air to be pumped into the ball when needed. The game is played between two teams with between 11 and 18 players on each team. The team that has the ball is called the offense and the other team is known as the defense. The goal of each team is to score by putting the ball into an opponent’s end zone or over a line.
The game begins with a coin toss which determines which team will receive the opening kickoff. The team that wins the toss will have possession of the ball at the beginning of the first half and at the start of each subsequent quarter. A team can also take over the ball by recovering a dropped or intercepted pass or by scoring a touchdown.
A player with the ball is called the quarterback. He or she can run with the ball or throw it to a teammate. Using different types of running and throwing tactics, the offensive team attempts to outmaneuver the defensive team in order to gain yards on the field. These strategies are called plays.
The playing field is 100-yards long with a 10-yard end zone for each team. A series of lines, called hash marks, mark the single-yard intervals down the field. A team has four tries, or downs, to advance the ball at least 10 yards. If they are unable to do this, the other team gets the ball. If the team does advance the ball, the downs reset and they can try again.
Penalties in football are designed to prevent certain actions that might give the opposing team an advantage or lead to dangerous situations for the players. Offensive penalties include grabbing or holding an opposing player, blocking below the waistline and a chop block. Defensive penalties include tackling the ball carrier or interfering with an attempted pass.
During the course of a game there are several ways that the clock can stop, for example when a player goes out of bounds or when a team calls a time out, of which they have three per half. The clock also stops during two-minute warnings observed prior to the end of the second and fourth quarters.
At the end of each quarter the winning team is awarded six points. In addition to this, a team can earn extra points if they make it over the opponent’s end zone or over a specific line. Depending on the situation, teams may also choose to punt the ball or try a field goal.