what is DRM:
Digital rights management
Companies such as Amazon,AT&T, AOL, Apple Inc., Google, BBC, Microsoft, Electronic Arts, and Sony use digital rights management.
Those opposed to DRM contend there is no evidence that DRM helps prevent copyright infringement, arguing instead that it serves only to inconvenience legitimate customers, and that DRM helps big business stifle innovation and competition. Furthermore, works can become permanently inaccessible if the DRM scheme changes or if the service is discontinued.