COM

From MDSN:

At a higher level, an ActiveX control is a COM object that implements several main ActiveX technologies, including regular incoming COM interfaces, the OLE embedding protocol, connection points, and property pages. At a lower programmatic level, ActiveX controls are just COM classes implementing certain families of interfaces. When some client code successfully queries for one of these interfaces, the client code then knows it's dealing with an ActiveX control.
The interfaces exposed by an ActiveX control fall into three general categories. First, ActiveX controls are embeddable objects; that is, they implement most of the OLE Document in-place activation and embedding protocols. ActiveX controls implement the following interfaces: IOleObject, IPersistStorage, IDataObject, IOleInPlaceActiveObject, IOleInPlaceObject, IViewObject2, and IRunnableObject (this is rarely used). Second, ActiveX controls usually support property pages so the client has a means of modifying the control's properties. Finally, ActiveX controls usually implement outgoing interfaces that the client can find out about using COM's connection point technology.

HakunaMatada wrote:

Dunno why I didn't look up MSDN