The CCompilerDriver package lets you work with C compilers that are installed on your computer. It lets you build executables, libraries, and object files from C source code. It is called automatically by the Wolfram System compiler when you set the option CompilationTarget to "C". It is also useful for building WSTP executables as well as Wolfram Libraries (dynamic linking libraries that can be linked into the Wolfram Language).
This library was written as a Wolfram Library, so you can load functions from it using LibraryFunctionLoad.
This calls the LibraryFunction.
The Wolfram System does not ship with a C compiler. If you want to take advantage of the CCompilerDriver package, you will have to make sure that you have an installed C compiler on your computer. Many computers either ship with a C compiler or can add one as an optional extra. In addition, you can find other compilers from various commercial and non-commercial sources.
You can learn about the C compilers that are supported in the section on specific compilers.