A COM object exposes one or more interfaces. Each interface consists of one or more functions. Strictly speaking, interfaces do not have properties. However, Visual Basic makes some of these functions appear as properties. Interface functions have input and output parameters and may have function return values. In later sections, we will show you how to call these interface functions to perform useful actions.
Interfaces sometimes have a hierarchy at work. An interface can inherit from another interface.
All interfaces are ultimately inherited from the IUnknown interface. Many of the DirectScript interfaces are dual interfaces, meaning that they inherit from IUnknown and a special interface called IDispatch. The IDispatch interface allows you to access methods of DirectScript objects using Visual Basic.