American football, known in the United States simply as football, is a competitive team sport that rewards players' speed, agility, skill, tactics, and brute strength as they run and throw a ball, and block, tackle, and outrun each other, trying to force the ball further into their opponent's territory and ultimately into the endzone.
It is one of the more physically demanding sports, with a great deal of physical contact occurring on every play as players often weighing 300 pounds (~135 kg) or more shove each other with all of their strength, and with a clearly defined front line, moving up and down the field, separating the offensive and defensive squads.
American football does not much resemble soccer, the sport which most people outside the U.S. call "football". Consequently, American Football is best known internationally as "American Football". However, both of these games have their origins in varieties of football played in the United Kingdom in the mid-19th century, and American football is directly descended from rugby football, usually known simply as "Rugby". According to an apocryphal story rugby football began with a football game at Rugby School in England in 1823 when a player named William Webb Ellis suddenly ran with the ball only to be tackled by an opponent. Contrary to popular belief rugby football had always permitted handling the ball but had banned running with the ball. Rule breaking gradually became increasingly common until it became the accepted norm. Thus was born the game of Rugby Football.
The game progressed from that point and was introduced to North America from Canada, by the British Army garrison in Montreal, which played a series of games with McGill University. In 1874, McGill arranged to play a few games in the United States, at Harvard, which liked the new game so much that it became a feature of the Ivy League. Both Canadian and American football evolved from this point. The U.S. game still has some things in common with the two varieties of rugby, especially rugby league