It's basically a rendering algorithm involving color bleed that radiates from one object to strike another, much like the way light bounces while absorbing color in the real world. 

Because of it's rendering speed and quality, it has become my favorite tool for photo-realistic rendering, which I use with SoftImage XSI. 

Among other things, I will showcase some of my best work. I will also show you how to achieve photo-realistic rendering in a couple of easy steps by using the final-gathering algorithm in the tutorial section.  Enjoy...