From http://www.wisegeek.com

DRM is an acronym for Digital Rights Management, a broad term used to describe a number of techniques for restricting the free use and transfer of digital content. DRM is used in a number of media, but is most commonly found in video and music files. There are many who argue that DRM is a misnomer, since it deals with use issues rather than the rights of the consumer. They therefore reinterpret DRM to stand for Digital Restrictions Management. The case for DRM is that without a strong system in place to ensure only paying consumers can access media, piracy will run rampant and cut drastically into profits for producers and distributors. With declining sales, so the argument goes, creative input will also drop and the overall quality of media produced will decline. Advocates for civil liberties argue that the use of digital technology should be unfettered, and that the shift of control to producers even after sales will ultimately hurt creative expression and damage consumer rights. Most media are protected by copyright, but have a fair use clause which allows for unhampered use in certain situations. All existing DRM technologies fail to adequately make concessions for fair use, leading many civil advocates to argue that they restrict the legal use of content. One of the first and most widely contested DRM systems was the Content Scrambling System (CSS) used to encode DVD movie files. This system was developed by the DVD Consortium as a tool to influence hardware manufacturers to produce only systems which didn't include certain features. By releasing the encryption key for CSS only to hardware manufacturers who agreed not to include features such as digital-out, which would allow a movie to be copied easily, the DVD Consortium was essentially able to dictate hardware policy for the DVD industry. Very quickly after the CSS DRM was implemented, its algorithm was broken. Tools such as DeCSS became available for making copies of CSS-encrypted movies and playing them on systems that otherwise would not be able to, such as some alternative operating systems. The Digital Millennium Copyright Act in the United States makes it illegal to use systems such as DeCSS to bypass DRM limitations. Similar acts have since been passed in many countries. Many advocates in the computer science world see the DMCA as a major blow against creative freedom because of its overly harsh restrictions. While DRM is most frequently used for movies, it is gaining more widespread use in other media as well. Audio files purchased through many online stores, such as Apple's iTunes Store, have various DRM schemes built in to limit the number of devices they may be played on. Many producers of eBooks are using a similar implementation of DRM to limit how many computers a book may be viewed on, and even how many times it may be viewed. In mid-2005, a number of content producers for television began requesting DRM of their shows via the popular TiVo system. Security issues, fair use issues, and issues of creative expression are all at the forefront of the DRM battle, and DRM technologies will undoubtedly be fought over for many years to come. While many within the media industry believe DRM is the only way to save their existing business model, predicated upon the idea of collecting a fee for each use, a number of innovators have begun exploring alternatives, anticipating an ultimate defeat for DRM.