In a .NET application, a runtime callable wrapper, also known as RCW, is an object created by the CLR to provide universal access to COM objects. Exactly one RCW is created for each COM object. When a .NET client makes calls to a COM object, the calls pass through the RCW as an intermediary object. This feature allows the client to access COM objects even if they were written in different languages.
CLR, Programming terms, Wrapper
