Studies of experts provide insight into what it means to have deep and flexible understanding. Experts in a particular domain are people who have deep, richly interconnected ideas about the world. They are not just good thinkers or people who are exceptionally smart. Rather, experts have knowledge in a specific domain ─ such as chess, chemistry, or tennis ─ and are not generalists. However, experts do not just know "a bunch of facts." In fact, having expertise in a topic means that knowledge is organized into coherent frameworks, and the expert understands the interrelationship between facts and can distinguish which ideas are most central. This kind of deep but organized understanding allows for greater flexibility in learning and facilitates application across multiple contexts.