>>283188421
>>283186777

3 Shaded anime is anime that tries to immigrate global illumination by separating colors into 3 parts that are supposed to provide depth information.

For example in OPs picture

The skin color and clothes directly in the sunlight are drawn one color
The part that obstruct the said sunlight are drawn in a dark shaded color
And finally parts that stick out and cast a shadow like his nose and mouth and eye sockets ears are drawn another even darker color.

If video game terms 3 shading in anime is basically RTX. It also functions like that too in the fact that it requires extremely skilled animators able to imagine global illumination and drawing it. So it ups the budget and time to produce a single scene.

This style used to be popular with OVAs and some anime back in the 80s/90s a lot of people remember this fondly because most of the best anime had it but it wasn't a universal thing.

TL;DR it adds additional 3d depth to images.