This book focuses on the technology of D-branes in Superstring and M-theory, presenting the main ideas and recent discoveries in a pedagogical manner. It will serve as an introduction to welcome and guide newcomers to this exciting field, and an indispensible reference for seasoned practitioners. The book starts by introducing the key features of string theory and the theoretical tools needed to get to grips with D-branes. It then builds up the subject in a logical way, discussing further aspects of string theory and advanced applications as the text progresses.