American football is a popular sport in the US, but it's also known as gridiron football, pigskin football, or just football. Gridiron football comes from the field markings, which resemble a grid, while pigskin football refers to the fact that the ball was originally made from pigskin. In Canada, it's called Canadian football, which has slightly different rules than American football. In some parts of the world, it's called tackle football to distinguish it from other types of football that don't involve physical tackles. Despite the different names, the game is loved by millions of fans around the world.