seeking veteran mac user wisdom

I have Onyx installed on my PB and I love it. I know that it tidies up my drive and performs all the maintenance that I need performed. I was looking for a site or a book, something that would explain, simply, exactly what it is that Onyx is doing. Something that would give it to me in simple terms what it means to repair permissions, what is a core.xxx file? What do the scripts do? etc.

The scripts are just maintenance scripts that you Mac runs all by it's self if you leave your computer on 24/7. They run somewhere between 3-5am I'm told.

You can run the same scripts through the Terminal window if you have them, I've seen them here on this board quite a few places.

You can also Repair Permissions with out Onyx as well. It's in Apps>utility>disk utility.

I don't know about the other stuff.. ?