Where are the lib and include folders in MinGW-W64 and why are there several of them?

Question

MinGW

Please explain, I can't figure it out.
In the compiler folder (MinGW-W64) there are lib and include folders, they are also in the x86_64-w64-mingw32 folder and are present in the opt folder.
Question: why are there so many of them and which libraries should I throw into (files .a and .h)?
And is it possible to do something so that there would be only one place with these folders, as in MinGW32?

Answer 1

To clutter up the compiler directories with your goodness is bad manners.
If edge, edit .spec file - www.mingw.org/wiki/SpecsFileHOWTO