ActiveX

ActiveX is a framework for defining reusable software components in a programming language-independent way (i.e. not tied to a particular programming language). Software applications can then be composed from one or more of these components in order to provide their functionality. It was introduced in 1996 by Microsoft as a development of its Component Object Model (COM) and Object Linking and Embedding (OLE) technologies and is commonly used in its Windows operating system, although the technology itself is not tied to it.

Many Microsoft Windows applications — including many of those from Microsoft itself, such as Internet Explorer, Microsoft Office, Microsoft Visual Studio, and Windows Media Player — use ActiveX controls to build their feature-set and also encapsulate their own functionality as ActiveX controls which can then be embedded into other applications. Internet Explorer also allows embedding ActiveX controls onto web pages.

Read more about ActiveX:  History, ActiveX in Non-Internet Explorer Applications, Other ActiveX Technologies