This introduction presents an overview of the concepts discussed in the subsequent chapters of this book. The book describes the theory and findings that constitute the four-phase model of interest development. It explains the historical context of educational and psychological studies of interest and the roots of different approaches to the conceptualization of interest. The book uses evidence from neuroscience to further clarify how learning, attention, and curiosity are related to interest. It defines the terms "motivation" and "engagement" and discuss their relation to interest and explains the links between interest and different types of motivational variables such as goals, self-efficacy, and self-regulation. The book considers the paradox of declines in interest as learners advance in schooling and discusses how interest is related to content knowledge, the relation between interest and identity, and the meaning of interest-driven learning. It provides readers with a research-informed follow-up to Dewey's now-classic essay that was published in 1913, Interest and Effort in Education.