Because we are in the US, I'm not going to call football "American Football" or whatever other people call our version of not-soccer outside of the USA. It's football here. That's the end of it. But I get it. To people who know football as some other thing or don't care to know our football as anything, the sport doesn't seem to make any damn sense. It's okay. It's as silly as America itself.
Just watch this hilarious animation explainer by Fraser Davison that goes through the basics of what you need to know about NFL football (it's all about taking land!). You'll have enough information to fake knowledge and drop jokes during the Super Bowl.