The conversation between human and AI assistant.
What are the most famous sports in the world? How are they played?
Can you tell me more about American football?
Sure! American football is a very popular sport in the United States. It's played by two teams of eleven players each who aim to score points by carrying or throwing a ball across their opponents' goal line. The game is split into four quarters, and each team can make a limited number of substitutions throughout the game. It's a very physical sport with players wearing helmets and protective padding.