ActiveX controls are small programs that are downloaded to allow your internet browser to run "some" internet application properly.
Example: VPN or remote computer connections through your browser, internet picture editing, online programs that do the job of other programs like Microsoft's internet exchange which acts as a internet version of Outlook email.
Now that you understand what activeX controls are, you can see that they
can be very dangerous especially if malware or viruses use them for harmful purposes,
but they can be very helpful for doing such things as I pointed out in the above paragraph.
Here is another angle on what activeX controls do: https://www.microsoft.com/protect/terms/activex.aspx
How to disable them:
"START" menu > "Control Panel" > "Internet Options" > "Security" tab > go down to "Custom Level" > scroll down to "ActiveX controls and plug-ins" > "Disable"
How to delete previously installed activeX controls:
Open "Internet Explorer" > "Tools" menu > "Manage Add-ons" > a list of activeX controls should come up and you can select any and press "Disable"
How to delete activeX controls in IE 7: https://pcsupport.about.com/od/fixtheproblem/ht/disableie7activ.htm
Hope this helped