The COM-callable-wrapper (CCW) is a .NET technique for COM interoperability. CCW wraps managed code as a COM object so that unmanaged code can call it like any other COM object. It effectively exposes a .NET managed class in any language as a COM interface. For more background, see the Visual Studio Help topic COM Callable Wrapper.
To expose a .NET class as a COM object, you configure the project so that the class is registered for COM interop. When you build the project, the class is registered and thereby made available to unmanaged COBOL.
All public methods defined and implemented in the .NET class are exposed as a COM interface. Your COM client application can then invoke those methods as if they were methods of a COM object.