HTML Help objects are special navigation controls for HTML Help such as splash screens, Related Topics, and shortcut buttons. ActiveX controls are reusable Microsoft HTML Help objects that add special functions to your topics such as calendar controls, charts, and banners.
HTML Help objects are really ActiveX controls specifically designed for HTML Help functionality. Examples of HTML Help objects include closing the viewer and displaying the HHCTRL version, which shows the version number for an ActiveX control used in a topic.
ActiveX controls are special applications that you can plug into your HTML Help project. They are designed to be small, precompiled, modular and reusable, and there is an ever-growing number of them available. Web developers have been using ActiveX controls to extend the functionality of their HTML pages and they can also be used by HTML Help authors to extend the functionality of HTML Help topics.