The term 'digital media' is contrastive - specifically, it is contrasted with 'analogue media'. This binary runs roughly in parallel with the distinction drawn between 'new' and 'old media', although, of course, new media are now not quite as 'new' as they once were. Technically speaking, where analogue technologies record signals as electric pulses (and usually to a fixed physical format, or intended for diffusion through such formats); digital technologies render those signals in binary form, as sequences of zeroes and ones. While the distinction is somewhat blurry, examples of analogue media include television, radio, vinyl records, video and audio cassettes, whereas examples of digital media include networked computers, mobile devices, and the huge array of 'suffixed' file formats (.mp3, .pdf, .jpg, .avi, .doc and so on). One way to distinguish analogue media is by their discreteness - you cannot play a tape or make a call on a television (it was not always so: early phonographs could be used for recording as well as playback, and early telephones were used to broadcast music). Digital media are metamedia, they remediate older media (Bolter and Grusin 1999), so you can email, read (write) the news, make a (video) call, read (and write, and publish) a book, listen to (and make, and distribute( music, download and watch (and produce) animation and so on, on a networked laptop. This is one of the meanings of 'media convergence'. More generally, digital media can be said to refer not just to the devices we use for producing, accessing, and distributing information, but to the cultural and social practices associated with their consumption, production and use, and indeed the political and economic ramifications of these.
History
Citation
Whelan, A. M. 2012, 'Digital media: the cultural politics of information', in B. M. Z. Cohen (eds), Being Cultural, Pearson, Auckland, New Zealand. pp. 333