It's not a simple thing, so don't worry. It took me a little while to understand and it wasn't without some head scratchers.

Best places to be are at discussion groups (api-craft, rest-discuss). Steve Klabnik has a good book on REST that explains it in more layman's term. Fielding's a PhD (REST was his thesis) so his writing is intended for an academic audience, it's indeed hard to follow without previous introduction.

I actually "understood" it on api-craft. The real-life examples it has are very helpful.