This chapter introduces the main topics of the book, and the field of AI and Games. The chapter gives a short outline of AI and games, including both academic research on AI applied to games, and developments in game AI from within the game industry. We then discuss how games, including video games as well as board games and other types of games, can be useful for AI research, as well as why AI can be used in game design and development. A key takeaway of this chapter is that there are a large number of applications for AI in games, many of them which are not about playing the games. The chapter finishes by presenting the structure of the book and outlines how to use it.