Four Link Suspension, how does it work?

Since suspension setup in these drag cars we run is what I consider to be voodoo magic can someone give me a Four Link for Dummies class? I was just beginning to gain a basic understanding of the ladder bar set up on the Dart I had previous, and now I have this Arrow with a four link set up. I hear things like 'pre-load' and 'instant center' and other terms like that and I just don't know what it means. I have no understanding of what moving the upper arms up or down, or moving the lower arms up or down does. I haven't touched a thing on the suspension of this car except to loosen or tighten the front shocks a couple of clicks per the recommendation of the previous owner as he told me that's all I'd ever need to do but I would like to have a working knowledge of what the four link does. Can anyone help?