Now, Im using Vray 3.4.
As I study by myself from youtube,
most of them use Mat ID, lighting, reflect , then blending in PS by screen, overlay or multiply.
Some of them use GI, raw light ,Raw reflaction , Raw reflection and so on..

I know that Mat ID can help us when we want to select something easier.
Light or reflect can make that image more brighter and more reflective, but what it's different and how can I use it between

Reflect and Raw Reflect
Reflact and Raw reflaction
Light and and Raw light

I checked from CHAOS, there are a lot of render elements https://docs.chaosgroup.com/display/VRAYSKETCHUP/Render+Elements
I dont know apply it when I use photoshop, of course I can find many clicps that teach render element,
but I cant not find criteria to use it.

sorry for my poor English

Thank you