CMAKE in Python script (slicer extension)

i’m building python script extension object.
but when I read document of python extension in slicer document, I look slicer require use Cmake to create .txt file in extension folder. but I still know role of cmake.txt in slicer extension.
when I down some code about python extension without cmake.txt file , it didn’t active.
can you explain role of Cmake in python extension help me?

thankyou so much!!

This post may help: Pure python extension: Packaging w/o CMAKE/Visual Studio, etc?