ActiveX is nothing but a small piece of code(better known as Add-ons), created by Microsoft. If you have Internet Explorer installed on your computer, then ActiveX is also installed. Purpose of this ActiveX is to improve the browsing experience but it only works with Microsoft applications like MS Word, Excel, PowerPoint, Internet Explorer. The Idea behind ActiveX is that same piece of code can be used in more than one place.
For Example, a spell checker functionality is required in MS Word as well as in e-mail application like Microsoft Outlook. So instead of writing same code twice, write a spell checking functionality in one place (i.e Windows Operating System) and call spell checker object wherever it is required.
ActiveX technology started as Object Linking and Embedding (OLE). In earlier version of windows, OLE used for cross application functions like Cut , Copy, Paste. Now a day, OLE has been transformed into Compound Object Module (COM). Spell checker is an example of COMs. It is an independent program in windows which can be used by any windows applications. ActiveX control is another COM which is used in larger applications.
For example, if you want to play flash files(.swf) in Internet Explorer, you need Adobe Flash player installed on your system first, as IE cannot play flash files directly. But if the whole website is built in flash and you don’t want to install Adobe Flash Player, then IE gives you an option to download and install Flash ActiveX at your OS level. After that IE can play the files in the browser itself.
As it is a piece of code, there is a risk of misuse also. Using ActiveX, applications/websites can access your personal information, also it could throw unwanted pop-ups. So before installing any ActiveX, make sure it is trust worthy.
How to install ActiveX ?
When any application needs ActiveX control, IE displays a dialog box asking your permission to install, provided Pop-Up blocker option in IE level is not set to ‘Yes’. Right click on the dialog box and click on ‘Install ActiveX Control’ option to install it.
How to uninstall ActiveX ?
Open Internet Explorer and then goto Tools > Manage Add-ons option. You can see the list of all add-ons, installed in your system. Select the ActiveX control you want to delete and then either click on Delete option or Disable.