Multimedia.

In other words - more than one medium. Integration of text, graphics, sound, animation, video and interactivity in order to make things we want other people to see clearer and more understandable.

On the Internet, fast development of multimedia begun after the World Wide Web had been introduced in early 90's. Browsers had the capability of integrating text and graphics, and allowed other non-supported digital formats to be viewed by invoking the associated helper applications - programs which could show/play/run previously downloaded file.
Later, another type of browser enhancements appeared - those which were able to teach browsers how to handle the unsupported file type by themselves.
They are referred to as plug-ins or add-ons.