Football is a sport played by two teams of 11 players on a 120-yard, rectangular field with goal lines on each end. A football is an oval-like inflated ball usually made of leather or rubber.
The offense, or the team with control of the ball, attempts to advance the ball down the field by running or passing the ball, while the opposing team aims to stop their advance and tries to take control of the ball. The offense must advance at least 10 yards in four downs, or plays, or else they turn over the football to the opposing team; if they succeed, they are given a new set of four downs.
The object of the game is for one team to outscore the other. This is accomplished by advancing the football down the field and scoring as many points as possible. Scoring can occur in the form of a touchdown, an extra point conversion, a two-point conversion, a field goal or a safety.
The time on the clock for a football game is 60 minutes. The game is divided into two halves of 30 minutes and four quarters of 15 minutes. The average duration of a football game is three hours due to the various clock stoppages that occur during the game.
The playing field is 100 yards long with a 10-yard end zone for each team. The field has stripes running the width of the field at 5-yard intervals. There are also shorter lines, called hash marks, marking each single yard interval down the field. The football field is 160-feet wide.
The spot where the end zone meets the playing field is referred to as the goal line. The goal line is the end zone, which is the same as saying the 0-yard mark. From there, numbers mark 10-yard intervals going up to the 50-yard line, which marks the center of the field. After reaching the 50-yard line, yardage markers descend every ten yards (40, 30, 20, 10) until they reach the opposite goal line.
Football features two teams playing against each other. Each team is allowed to have eleven men on the field at any given time. More than 11 players on the field results in a penalty. Unlimited substitution is permitted, but players can only enter the field when the ball is dead and play is stopped.
Each team has offense players, defense players, and specialized players, called "special teams." If a team has possession of the ball, they are considered to be on the offense and use their offense players to attempt to run with the ball or pass the ball forward toward the opponent’s end zone. Meanwhile, the other team, considered to be on defense, will use their defense players to attempt to stop the other team from advancing the ball. If a kicking play is expected, the teams will use their special teams units.
The game begins when one of the teams kicks off the football to the other. The captains from each team and the referee meet at the center of the field for a coin toss to determine which side is the kicking team.The winner of the coin toss has the option of starting the game by kicking the ball to the other team or receiving the kickoff from the other team, essentially deciding if they want to be offense first or defense.
The receiving team must catch the ball and try to advance the ball toward the opposite end of the field to the other team's end zone. The play, or down, ends when the ball goes down to the ground or the ball goes out of bounds. The place where the ball goes down becomes the line of scrimmage, and it is where the ball is placed for the start of the next play. The offense is given four attempts, or downs, to gain 10 yards or more. Upon achieving 10 yards, the offense is awarded four more attempts to achieve 10 or more yards and play continues like that until the offense scores or the defense regains possession of the ball.
The biggest goal for the offense is to score a touchdown. To score a touchdown, a player must carry the ball across the opposition's goal line or catch a pass in the end zone. Once the ball crosses the plane of the goal line while it is in a player's possession, it is scored a touchdown. A touchdown is worth six points. The team scoring a touchdown is given the bonus of trying to add one or two more points. These are called extra-point conversion attempts.
If a team elects to go for two extra points, they will line up at the two-yard line and make one attempt at either running or passing the ball into the end zone. If the team makes it, the team is awarded two points. If the team does not make it, then no extra points are awarded. The team can also elect to go for only one extra point by kicking the ball through the goal posts from the two-yard line, a generally safer and more efficient scoring method.
Field goals are another way for a team to score points in the game. A field goal is worth three points. A team in a fourth-down situation might decide to attempt a field goal, which means the team feels that its special teams' kicker is within a comfortable range of kicking the ball between the upright bars of the goal post in the opponent's end zone.
A team can also pick up two points by tackling an opponent possessing the ball in the opponent's end zone. This is called a safety.