Somebody Please give me a starting point to understand custom ROMs etc.

[ocbizlaw]

I've seen some hacks here along with some custom programs and I've tried them but I'm a beginner and I'd like to understand more. For example, I just saw the there is a new Juicy ROM out and that it helps battery life and speed. I'd give it a try and I could unlock my phone and install it. I can get that far, but I don't know what happens to TF3D, Sprint software likd Sprint Navigation and TV. And I don't know how to reinstall my original Sprint ROM if I want to go back. I've searched the posts here and I can't find a basic overview of all of this. Is there a basic primer on this stuff? If so, where can I find it?

Please don't flame. I'd just like to get an overview and try to understand this all better.