Introduction You are about to begin your study of economics. Before we start discussing particular topics in economics, we think it best to give you an overview of what economics is and of some of the key concepts in economics. These key concepts can be compared to musical notes: just as musical notes repeat themselves in any song (you hear the musical note G over and over again), so do the key concepts in economics repeat themselves. Some of the key concepts we discuss include scarcity, opportunity cost, efficiency, marginal decision making, and exchange.