ActiveX is Microsoft technology used for developing reusable object oriented software components. ActiveX is an alternate name for OLE automation, not a separate technology. While the term "Automation" refers to the overall technology, "ActiveX" refers to the objects that can be created and manipulated using Automation.
Due to Internet Explorer and Visual Basic's popularity in the late 1990s, many people incorrectly assume that all of ActiveX is related to ActiveX controls. An ActiveX control is a special type of ActiveX object that is designed to be used similar to a plugin. The most common use of ActiveX controls is to build plugins for Internet Explorer.
Technologies using ActiveXMicrosoft has developed a large number of products and software platforms using ActiveX objects, and many are still in use today.
a) ActiveX Data Objects (ADO)
b) Active Server Pages
c) ActiveMovie, later renamed to DirectShow
d) Active Messaging, later renamed to Collaboration Data Objects
e) Active Scripting, a technology for scripting ActiveX objects.
f) ActiveX Streaming Format (ASF), renamed to Advanced Streaming Format, then to Advanced Systems Format
An ActiveX control is similar to a Java applet. (
see Best Java Hoster). Unlike Java applets, however, ActiveX controls have full access to the Windows operating system. This gives them much more power than Java applets, but with this power comes a certain risk that the ActiveX control may damage software or data on your machine. To control this risk, Microsoft developed a registration system so that browsers can identify and authenticate an ActiveX control before downloading it. Another difference between Java applets and ActiveX controls is that Java applets can be written to run on all platforms, whereas ActiveX controls are currently limited to Windows environments,
see Windows Hosting) 
