This chapter explains the fundamental principles of audiovisual content protection. It explains the basic knowledge that is needed to understand the fundamentals of digital rights management (DRM) systems and their problems. Starting with a general introduction about copyright and content protection, available protection technologies are described and analyzed. The basic concepts of DRM solutions are explained and problems discussed. Potentials and practical limitations are analysed based on the digital music industry value chain. An outlook is given on solutions that are under development and that stronger consider the needs of the customers. In the conclusion, future solutions are discussed.