Cg lighting breakdown

I’ve been watching people light breakdowns on youtube of there models and I was wondering how would I learn this?

By this, there demo will show diffuse pass, occlusion added, key pass, zdepth, BG added, color correction and so on. Not sure if this is compositing or what? Either way i can’t find a tutorial on this stuff.

I’d guess that they take their different passes (or Progress stages) as normal Pictures or Clips and animate them ontop of each other in a movie editing program. (i imagine doing this in after effects, premiere or even blender).