[Question] How to use Tessellation ?

I'm a beginner in this subject. I try the scripts in the document manual
https://docs.unity3d.com/Manual/SL-SurfaceShaderTessellation.html
but are not Physical base shaders and makes holes in my 3d the geometry.

I try a bit using Amplify visual scripting and there is a Tessellation input but I was not able to include roundness as I was expecting and the example looks to work well with a flat surface and image.

I also try ShaderForge with no much success. Look like was not made in PDS

Do I need to back my hi poly mesh a displacement texture and use the low poly and apply tessellation on it?

As I mention pick me as an absolute beginner in this subject.
What is the main use and how to use it?


EDIT: Same links
Here is a Uinty5 tessellation metallic PBR setup https://pastebin.com/quZSxe0C