Computer Systems - Background Check

What do you already know about computer systems?

I know little to nothing, despite the endless time consumption devoted to the use of my computer. So, my glass is pretty empty, and could use a nice dose of hard knowledge.
Terminology: an endless list of terms regarding the operating system of a computer, physically and virtually. I may be fairly virtually aware, but physically... well... lets just say I haven't learned that stuff quite yet. I've played over Local Area Networks using Warcraft III and Age of Empires II, but that's basically it, really. Everything else, I'm... fairly ignorant.

What do you want to learn about computer systems?

Mainly, I want to learn about networking and such. Everything else, you can pretty much just throw at me and I'll do my best to absorb it.