What is media?
Media:
Origin: 1921
Until the Roaring Twenties, a medium was a person, not a publication, and media--well, there wasn't such a thing. The medium would set bells ringing and tables hopping in a darkened room by conjuring connections with departed spirits. And media was just an obscure Latin plural of medium.
Then came modern advertising and a sense of media that had nothing to do with the sphere of the spiritual. Suddenly in the advertising world it was smart to speak of placing ads in different media, or in one particular media, the word being used as a singular as well as a plural. This new media has been traced as far back as a 1921 play by two smart members of New York City's Algonquin Round Table, George S. Kaufman and Marc Connelly. In advertising, the new plural medias also was coined. Advertising professionals were reported in 1927 as stating, "It was finally decided to allot a definite media to each member," and touting "one of the best advertising medias in the middle west."
The original means of mass communication were print: magazines, journals, and newspapers. A collective name for them was already available: publications. Then radio and television were added to the mix, and publications would not stretch to fit. Needing a term to encompass them all, we borrowed media from the advertising people and have used it ever since, ready to accommodate newer media like the Internet. We have also used the term to refer to journalists as a group or the communications industry as a whole. How else could we put it nowadays than to say that the media have a profound influence on our lives?
from http://www.answers.com/media
Also see definition 2 here:
http://dictionary.reference.com/browse/media