Digital rights management technologies attempt to control or prevent access to or copying of digital media, which can otherwise be copied with very little cost or effort. Copyright holders, content producers, or other financially or artistically interested parties have historically objected to copying technologies, even before the advent of digital media. Examples have included player piano rolls early in the 20th century, audio tape recording, and video tape recording (e.g. the “Betamax case” in the U.S.). Digital media has only increased these concerns. While analog media inevitably loses quality with each copy generation, and in some cases even during normal use, digital media files may be copied an unlimited number of times with no degradation in the quality of subsequent copies. The advent of personal computers, the ease of ripping media files from CDs or from radio broadcasts, combined with the internet and popular file sharing tools, has made unauthorized dissemination of copies of digital files (often referred to as digital piracy) much easier. This has concerned some digital content publishers, leading them to pursue DRM technologies that attempt to prevent those actions.
Although technical controls on the reproduction and use of software have been intermittently common since the 1970s, the term DRM has come to primarily mean the use of these measures to control copyrightable artistic content. As cited above, some observers claim that certain DRM technologies enable publishers to enforce access policies that not only prevent copyright violations, but also prevent legal fair use.
While DRM is most commonly used by the entertainment industry (e.g. film and recording), it has found use in other media as well. Many online music stores, such as Apple‘s iTunes Store, as well as certain e-book publishers, have adopted various DRM strategies in recent times. In recent years, a number of television producers have begun demanding implementation of DRM measures to control access to the content of their shows in connection with the popularity of time-shifting digital video recorder systems such as TiVo.
Source : wikipedia