An ActiveX control is essentially a simple OLE object. Originally, ActiveX controls were called "OLE controls" and used a .ocx file extension. This was actually the second-generation component architecture. The first generation was the Visual Basic Controls (.vbx). OLE controls were renamed ActiveX and continue to use the .ocx extension. ActiveX controls enable a program to add functionality by calling ready-made components that blend in and appear as normal parts of the program. They are typically used to add user interface functions, such as 3D toolbars, a notepad, calculator or even a spreadsheet.

Within the context of a compatible web browser, ActiveX controls can be linked to a web page and downloaded by the browser. These controls turn web pages into software as if the program was launched from the server. As with any executable program, ActiveX controls can perform data operations. This is why the default configuration for most web browsers is to prompt the user if an ActiveX control is being requested so that the user can decide whether or not to run the control.