Football is a family of team sports in which the object is to get the ball over a goal line, into a goal, or between goalposts using merely the body (by carrying, throwing, or kicking). Unqualified, the word football generally means the form of football that is the most popular where the word is used. Sports commonly called football include association football (known as soccer in Australia, Canada, South Africa, the United States, and sometimes in Ireland and New Zealand); Australian rules football; Gaelic football; gridiron football (specifically American football, arena football, or Canadian football); International rules football; rugby league football; and rugby union football. These various forms of football share, to varying degrees, common origins and are known as "football codes". There are a number of references to traditional, ancient, or prehistoric ball games played in many different parts of the world. Contemporary codes of football can be traced back to the codification of these games at English public schools during the 19th century, itself an outgrowth of medieval football. The expansion and cultural power of the British Empire allowed these rules of football to spread to areas of British influence outside the directly controlled empire. By the end of the 19th century, distinct regional codes were already developing: Gaelic football, for example, deliberately incorporated the rules of local traditional football games to maintain their heritage. In 1888, the Football League was founded in England, becoming the first of many professional football associations. During the 20th century, several of the various kinds of football grew to become some of the most popular team sports in the world.
The two teams will play a 60-minute game, broken into 15-minute quarters. After two quarters are complete, the teams will take a halftime break lasting approximately 20 minutes. Teams will change direction of play after every quarter, in order to correct any unfairness due to the wind blowing strongly in one direction of the field. To start any play, 11 offensive players and 11 defensive players line up against each other. The play starts when the center, an offensive player, throws the ball backward between his legs to the quarterback, who snaps the ball. The line where the ball starts on each play, which is also the line separating the offense and defense, is called the line of scrimmage. Football is structured into drives. The offensive team will start at the yard line where they return the kickoff, or the 25-yard line should the kickoff result in a touchback. The first down marker is placed 10 yards beyond where the drive starts, and the offense has four tries, known as downs, to reach that marker. If they fail to do so, the other team will take over possession of the ball from wherever their opponent’s drive ended. If a team reaches the first down marker within their four tries, the marker is moved another 10 yards and the team gets a new four tries. If a team has used three of its downs and has not earned a first down, it will likely use its fourth down to punt, or kick the ball downfield to its opponent, rather than risk giving the other team the ball in an advantageous spot on the field.