This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book defines digital media, identifies fundamental tendencies in digitization and revises the theoretical fields, which can be considered a "tool box" for students looking for a well-founded historical interpretation of the digital media phenomenon. It discusses the specific histories of three main digital media: computers, internet, and mobile phones. The book analyzes the emergence of the digitization process in relation to six specific sectors: music, books and news making, cinema and video, photography, TV and radio, tracing the main tendencies through which the digitization developed in each. In addition to the diachronic dimension, it considers two other fundamental guidelines and perspectives: an intermedia approach and a distinctive sensitiveness to the global range of digital media development. The book also discusses the need to consider digital media in its mutual and recursive interaction.