As the name implies, multimedia is the integration of multiple forms of media. This includes text, graphics, audio, video, etc. For example, a presentation involving audio and video clips would be considered a "multimedia presentation." Educational software that involves animations, sound, and text is called "multimedia software." CDs and DVDs are often considered to be "multimedia formats" since they can store a lot of data and most forms of multimedia require a lot of disk space.
Due to the advancements in computer speeds and storage space, multimedia is commonplace today. Therefore, the term doesn't produce the same excitement is once did. This also means it is not as overused as it was back in the late '90s. Thank goodness.