Football?

I don't get football.
First of all, as a kid I was never big enough to get picked anywhere before the last draw. And when I did get picked I was never given a position of great importance so I never had to learn the rules. It just seemed to me like an organized way to bully smaller kids with the sanction if the administration.
I never quite got the hang of all the rules. I mean I know the very basics but that's it. I can't follow the action on the screen when I try to watch a game with friends.
I do know some of the rules:
The players are divided into a bunch of various positions of (fraction)-backs. The greater your fraction the larger you are and the less you actually get to touch the ball. Fullbacks are the biggest guys out there but they rarely get to touch the ball. The quarterback is one of the smallest players and he touches the ball every single play.
They also have a position called the kicker. Ironically, for a sport that is called football this seems to be the only player who actually gets to touch the ball with his foot.
The basic idea, as I understand it, is that your team gets 4 chances to move the ball a specified distance. If they succeed they get 4 more chances to move it an additional distance. If they fail the ball is given over to the other team. If they make it to the other side they get 6 points and then the kicker can help them get an additional point.
I know that there are times when they can kick the ball from various parts of the field to get 3 point, but I have no idea what the rules are surrounding this.
There is also something called a safety that gets 2 points. I have no idea what that is or how you earn it.
There are all sorts of penalties and things that the referees can penalize a team with but, again, I don't know what any of them are or how they are assigned. They are times when flags are thrown in the air. I have no idea what this means. Taken in context I don't think flags are good things.
Friends of mine will try to talk football with me and I honestly think they don't believe me because they keep on talking about it as if I understand. Last week a friend asked if I had head the news a specific player but didn't identify him as a football player. "Hey did you hear about so-and-so?" I thought he was asking about a coworker. He then began to belittle me when I told him that I didn't even know who so-and-so was, let alone had I heard the latest news. For that few seconds I was back on the elementary school playground being picked last again.
I really don't have any beef with football as a sport. I might even enjoy watching it with some friends as long as they could accept the fact that I really don't understand it. The few times friend have attempted to explain it to me they've quickly grown frustrated by just how little I know and given up.
So in the future if any of my readers wants to talk about football, be advised that you will have to give a lot more background detail in order for me to understand what you’re saying. As long as you're cool with that I'll do my best to follow along.