This is a Cartoon Shader Material Guide.
There are actually many different ways to do it. Epic Games Korea alone has introduced as many as five methods.
Because of that, it’s hard to say which one is the “standard” approach.
So I hope you’ll view this as “here’s one way you can do it.”
https://dev.epicgames.com/community/learning/tutorials/bB4n/unreal-engine-cartoon-shader-material-guide