IMHO, the best way to think about RPG's is to remember your childhood on the playground...
You're playing Cops and Robbers (or whatever variant you like). You're having fun. One group is cops, another is robbers, and you're all running around going "bang, bang, you're dead!"
But, inevitably, a fight breaks out. "I shot you!" "No you didn't! You missed me!" "Did not!" Did too!" Etc., etc., etc.
The purpose of a role-playing game is, in essence, to determine whether or not you really did shoot him, or whether you missed.
So, you get a bunch of rules, about how good you are at shooting, how good they are at dodging, and how to introduce a little luck and chaos to keep things interesting. (That's where the dice come in. They represent all the stuff that neither character can really control.)
Now, there's a lot of stuff to do besides shooting. There's running and jumping. And talking and schmoozing. And, of course, magic. So, we get a bunch of rules for those things, too.
Bad rules are very complicated, unbalanced, and don't represent the story well. Good rules make it so that your character does exactly the sorts of thing you think he ought to do.
We're waiting on Evil Hat to deliver unto us...the Good Rules.