What is the difference between an Interop and a RCW (Runtime Callable Wrapper)?

Question

What is the difference between an Interop and a RCW (Runtime Callable Wrapper)?

Is it just terminology?

Answer 1

They are connected with each other. Interop is the overall term for using native dll's within .NET. A RCW is a wrapper which is needed to use one specific component/class/object in .NET.

Answer 2

Interop is for calling raw DLL exports.

RCW (Runtime Callable Wrapper) is used to expose COM objects to .NET classes - ie., to make COM objects callable by .NET code. The RCW is a .NET proxy that uses interop to interface to the COM object.

You could use Interop directly to COM, but that's just doing it the hard way.