The building blocks of human cognition are concepts. What we see, hear, interpret, remember, understand, and talk about is crucially shaped by our concepts. They allow us to communicate, categorize objects and events into inductively powerful groups, organize our world, construct complicated thoughts, and conserve memory resources. Alternative theories have proposed that concepts are represented by rules, prototypical category members, many specific exemplars, and structured theories. We consider empirical evidence bearing on these proposals, which, on balance, recommends pluralism, with different representations implicated in different situations. We consider ways in which concepts shape, and are shaped by, perception and language. Concept‐learning research has important educational applications for helping students learn concepts in an efficient and generalizable manner, and we review what is known about how best to improve concept‐learning outcomes. Finally, we consider future directions for research on concepts and categorization, emphasizing links to other fields, such as object recognition and developmental psychology, and the development and testing of computational models.