Digital Restrictions Management

DRM stands for "Digital Rights Management", or to its opponents "Digital Restrictions Management."  

DRM is a general term for any kind of technology that a publisher, content provider, or device manufacturer uses to restrict the full use of the product.  

Such restrictions are typically placed on a product in an attempt to protect a content holder's copyright, and is in most cases used to prevent or deter "unauthorized" duplication or distribution or content.

While the most prevalent examples of DRM are found in the Music industry, the use of DRM is gaining ground in other arenas.  

Product Activation in software is a form of DRM, and is quickly becoming one of the most common forms.