These are the C++ API functions available in UE4SS, on top of the standard libraries that C++ comes with by default and the reflected functions available in Unreal Engine.
You are expected to have a basic understanding of C++ and Unreal Engine's C++ API before using these functions.
You may need to read code in the UEPsuedo repository (more specifically, the include/Unreal directory) to understand how to use these functions.
For version: 3.0.0.
Current status: incomplete.