Thread: What parts are there to the C language?

I recalled making a multithreaded program but forgot if I used C or C++. When I google searched if C is multi-threaded I came across this stackoverflow post.

"C is not intrinsically a multithreaded language; however there are many libraries which add threading functionality."

I don't understand because <math.h> is a library, so does that mean C doesn't intrinsically have a function for raising a number to the power of another?

When I did multithreading with a program written in C we used pthreads. I know pthreads are supplied by the operating system. I guess my question is where is <math.h> supplied, is it already known by all C compilers?

If something is part of the C standard library does that mean any C compiler must support it?