The nature of chess has been often debated in the literature. Chess has been the topic of much scientific research. Chess has been investigated by a number of academic disciplines, including sociology, ethnology, philosophy, mathematics and neuroscience. Chess psychology is an active domain of research and is arguably the main domain in expertise research. In artificial intelligence, chess has been a standard task for the development of machine learning and search algorithms. Many different aspects of chess are studied, from cognition to personality to intelligence. Combining experimental methods with ideas from artificial intelligence and computational modelling, Herbert Simon and William Chase performed a series of experiments that inspired much of the research carried out. The key study in chess psychology, carried out by Simon and Chase in 1973 at Carnegie Mellon University in Pittsburgh, developed a powerful theory. The chapter also presents an overview of the key concepts discussed in this book.