Windows API

I’m a bit confused about all the terminology Microsoft is throwing out. What are the components of the Windows API for programming? I’m not sure if it’s the .NET framework because that seems to have a lot of things. And it wouldn’t be a native API because users have to install the framework at one time.

I know Mac OS X has like graphics rendering component API’s for programmers. What are some of the equivalent for Windows? Graphics, networking, etc. Are they just pre-compiled code libraries? Are they written in C++?