Football is a team sport in which 11 players play on each side. The offensive team tries to move the football forward as far as possible during their four downs. If they fail to do this within those four downs, they are called for a turnover. The offensive team then has 4 downs to move the ball as far as possible before the other team takes it. When the offensive team runs out of time or fails to move the ball far enough, they must punt the football, and the defensive team has the ball.
Football originated in ancient Australia, where indigenous people played a variety of kicking and catching games with stuffed balls. This game was later generalised by historians as “Marn Grook” (Djab Wurrung, or “game ball”). The earliest historical account was an 1878 book by Robert Brough-Smyth, who was an explorer who discovered Australia. He was quoted as saying that Aboriginal people had played a game in 1841 in Victoria with a possum skin ball. Many historians believe this is the precursor to Australian rules football.
The rules of football have many variants but essentially all games have a similar origin. A touchdown is a score for the offensive team, and occurs when a player carries or receives the ball into an end zone. A safety can also be scored on a passing play when the quarterback is sacked and cannot throw. During the course of a game, the offensive team may also turn over the football accidentally. This can happen in two ways: either when a player on the offensive team tackles the opponent inside their own end zone, or when a defensive player is able to make a tackle with the ball carrier.