A Brief History of COM
To learn the details of COM interoperability within the CLR, you must first understand the fundamentals of COM. This section provides a quick primer on COM for those readers who never learned about it or who might have forgotten some of the details. If the details of COM's inner workings are still fresh in your memory, feel free to skip ahead to the next section.
A COM DLL serves up objects through creatable classes known as coclasses. A client application creates an object from a COM DLL through a process known as activation. A client application must activate a COM object from a coclass before it can begin to execute the object's methods.
COM does not allow a coclass to expose public methods. Instead, a coclass can expose ...