Primary problems

I like CNN's summary of the candidates and the issues. Simplistic for a real analysis, but helpful for me.

John Kerry. I don't trust him. I don't trust his hair. I don't trust that he supported the war. But I really don't trust his hair.

John Edwards. Seems like a really nice guy. Solid. Too bad it sticks in my mind that he supports the death penalty.

Wesley Clark. Not blinking. That's it. That's why I find Wesley Clark creepy.

Howard Dean. The media's done a real job on Howard Dean, making him Internet king, then criticizing The Speech, and bankrupting him. If I were conspiracy-minded, I'd blame the media for Dean's rise and fall. I still like him. I liked him since the day he came out against war. And I liked the speech. I don't think it was inappropriate; it showed passion. All the other guys say stuff, but it's hard to believe they mean it.

So, really — Can someone please explain to me how the primaries work? What's the difference between a primary and a caucus? And why is it so difficult to find out the answers to these questions?