According to history American football came into being in 1869. The first game took place between Rutgers and Princeton University. In American football the main idea is to carry or throw the egg-shaped leather ball in the opponents’ end zone.
The rules of American football
Every team is specialized in either offense or defense. For each game play versions there are 11 players available.
One cannot really compare American football to football or rather soccer in Europe, perhaps more with the strategy game chess. The crucial issue is with which plays the attacking team will outdo the defending team. To be able outsmart the line of defense, the attacking team has to get the ball at least 10 yards beyond - including the ball -, to be able to remain in the attacking mode. And to even be able to achieve the space of 10 yards, the "offense" gets four tries by running and passing game moves (first down, second down etc.). The "defense" tries to tackle the player who has the ball or to get ball themselves (fumble).
Points are only scored when the attacking team gets the ball into the opponents’ end zone. In exceptional cases the defending team can also score points, but only if they catch a ball that is thrown and bring it into the end zone of the attacking team. This is called an "interception". If the ball gets to the end zone six points are scored and is known as a "touchdown". Each touchdown is followed by the possibility to score another point, the so-called "field goal". To achieve the field goal there is an especially qualified player – the "Kicker". The kicker is comparable to a free kick specialist in soccer. The only difference is that there is no opposing wall in the way. An extra point after the touchdown can only be given to the team if the ball it shot through the goal, which is formed like a "U" and has two poles that are three meters high, from a distance of several meters away. If the attacking team does not accomplish a touchdown in the third down, then often the fourth down is used to try to achieve a field goal. If the shot is successful, three points are scored.
NFL - National Football League
The game consists of four play periods which are called "quarters". The playing time of one quarter is 15 minutes long. The National Football League (NFL) has 32 teams in total, which are divided into eight groups which each have 4 teams. The teams compete against each other within the groups and also outside of the groups according to a complicated allocation procedure for league games.