The difference should be

Shen Jing layer

depth

Simulate the bright and dark layer of skylight

occlu

Normal direction layer

normality

Object mask layer

companion

Object color layer

Div

High gloss layer

Mirror

Shadow layer

shadow

I believe that once you try, you will understand the rest.

Shen Jing layer

Use black and white to show the foreground of the object in the camera.

Easy to adjust the distance, reality, etc.

Normal layer

It uses rgb color to indicate the direction of object discovery, which is convenient to adjust the color of light in synthesis.