Can someone explain FakePCIID and FakeID to me, preferably in detail?

Hi there. I've already hacked my current system, and I am considering buying a new system, which I also intend to hack. My last system took a lot of trial-and-error, and a lot of wild guessing. But I'm satisfied with what I've got in my hands.

I want to do it right this time. One of the things for which I'm still in the dark, is graphics. I don't quite understand the FakeID in Clover (you know, IntelGFX FakeID...) and the FakePCIID. I used FakePCIID kexts to enable QE/CI for my current hack (Haswell iGPU). I remember that there are quite a few kexts that come with the FakePCIID package. I'll appreciate any explanation for the working of these features, when to use them, and the proper way of using them. Thanks :D