Wiring questions please help.

[LowchevyII]

Ok, so im in the process, well rather about to begin the process of rewiring my car. Ive been thinking about going with the AAW highway 22 kit. Seems like a real bang for the buck there. However, i forget where i saw it, but i saw in a picture of a build up that they had wired up a Dedenbear Multiple relay center and used that for accessories such as rad. fan, ignition, etc. I was wondering why that is. I also see on a lot of DSE's projects they have the same fuse type looking things under the dash also labeled for the same things. Just curious what those are for.

Next question is what is the ISIS wiring stuff and how does it all work?

thanks in advance

jeff