Digital Rights Management
Aka: Copy Protection
Any system that creates and limits a user's ability to make use of digital content. The major hurdle for the industrial development of such a rights system is to adopt standards and mechanisms that the average user finds acceptable. Because it is a restriction on consumers and consumers ultimately chose how they receive media, this has been a struggle to adoption.
DRM, copy prevention and copy protection may be used interchangably. It includes the legacy methods such as code wheels and manual page/paragraph/word lookups that comes bundled with some software and was needed for the program to run properly.