Economics is the study of how individuals, businesses, governments, and societies allocate scarce resources to satisfy unlimited wants. At its core lies the fundamental problem of scarcity, the recognition that productive resources are limited while human desires are essentially boundless. Because resources cannot meet every want, every choice carries an opportunity cost: the value of the next best alternative that must be given up. Thinking in terms of opportunity cost is the cornerstone of rational decision-making, and it forces analysts to confront trade-offs explicitly rather than treat choices as free.
Economists commonly divide their discipline into two branches. Positive economics describes what is, relying on facts and testable statements about how the economy behaves. Normative economics, by contrast, addresses what ought to be, incorporating value judgments and opinions about desirable outcomes. Positive claims can in principle be confirmed or refuted with evidence; normative claims cannot. A related distinction separates microeconomics, which studies individual markets, households, and firms, from macroeconomics, which examines the economy as a whole, including growth, inflation, and unemployment.
Two additional tools help organize economic reasoning. The production possibility frontier illustrates the maximum combinations of two goods an economy can produce given its resources and technology. Points on the curve are efficient; points inside represent inefficiency; points outside are unattainable without growth. Marginal analysis, comparing the additional benefits and costs of a small change in activity, guides rational choices wherever marginal benefit equals marginal cost. Closely related is the concept of utility, the satisfaction derived from consuming goods, and the principle of diminishing marginal utility, which states that each additional unit of a good yields less extra satisfaction than the one before.