<human>:  What is the difference between American football and rugby?
<bot>: The main difference between American football and rugby is that American football is played with an oval-shaped ball and involves players wearing pads, helmets and other protective gear while rugby is played with an oval-shaped ball and players do not wear any protective gear. American football also has a greater number of players on the field at a time, typically 11 on offense and 11 on defense. Rugby has fewer players per side, normally 15, and those players must be able to play both offense and defense. In American football, the main goal is to score touchdowns by crossing a goal line set at the end of the field; in Rugby, the main goal is to score points by kicking the ball between the two posts (a conversion) or through the posts (a penalty kick or a drop goal).