Honestly, you probably don't really need to understand it. It's pretty much a dead genre at this point, at least in terms of having mainstream fantasy published in that genre. People keep recommending Howard, Lieber and Moorcock because no one else is writing stuff in that vein anymore.I guess, but it seemed by the others that it couldn't be explained without that knowledge, which would tell me I need a rather in-depth knowledge of the subject matter to even start getting an idea. Far more than a simple summary.
They might have been wrong about how much I needed to understand Greyhawk, but I would say that to understand the Genre I probably need more.