представление надстройки(In the .NET Framework add-in programming model, an assembly that contains interfaces or abstract base classes, and represents the add-in's view of the methods and types used to communicate with a host)
представление надстройки в основном приложении(In the .NET Framework add-in programming model, an assembly that contains interfaces or abstract base classes, and represents the host's view of the methods and types used to communicate with an add-in)