ActiveX is technology of prewritten software that developers can use within an app or a webpage.
The tech was launched by Microsoft in 1996 and is part of the OLE and COM frameworks.
By implementing ActiveX, developers can add much-needed layers/functionality to their apps/site without the need to re-write code or hire programmers to code from scratch.
Add-ons are called ActiveX controls but can only be run on Microsoft's own Internet Explorer.
Examples of ActiveX controls are streaming stock tickers, clocks, countdowns, games, text boxes, pop ups, and more.
ActiveX is notorious for being used as a way to spread malware and therefore is not generally accepted and mostly blocked.