MS Automation Things Known To Me Until Now

1. VS IDE Automation Model. It's a set of API that can visit everything in VS IDE. VS addin is developed with the assistance of it.

2. MS UI Automation Model. It's a set of API (separate ones for C++ and .Net languages) that can be used to visit a window and mimic UI operation to UI controls.

3. Visual C++ Extensibility Object Model 

The Visual C++ Extensibility Object Model is a set of COM objects, interfaces, and associated managed wrappers that can be used with any language that complies with COM or the .NET Framework to automate actions occurring in the Visual Studio integrated development environment (IDE). 

http://msdn.microsoft.com/en-us/library/174179de%28VS.80%29.aspx 

Example: Generate and examine Visual C++ code by using a Visual Studio add-in written in Visual C#.