The book is a guide to understanding the economic impact of digital technologies and, in particular, of the Internet, which is analyzed both as a media and as an industrial platform, with an original reading of its historical evolution and its trajectories. Digital markets, with their perimeters and their sizing, are described analytically by means of a new representative model (LIIF), which allows a mapping of supply and demand, as well as a taxonomy of products-services, making it easier and systematic knowledge of this industry and its sectors is accessible. The volume also makes use of economic theories such as those of platforms and multi-sided markets to explain phenomena such as concentration in a few global player.