What is "api-ms-win-core-..."?

Question

I have 2 questions regarding those DLLs:

1. Why do they exist? I can see that all they do is have exports that forward to functions in other modules like Kernel32 or NtDll

2. When I use LoadLibrary with one of those modules, it ends up loading something called "KernelBase.dll". What is that and why is the actual module not loaded?

Thanks!