This study guide introduces fundamental economic concepts including microeconomics, macroeconomics, the three basic economic questions, scarcity, economic systems, factors of production, wants and needs, barter, opportunity cost, the laws of demand and supply, goods and services, fixed and variable costs, consumer sovereignty, the circular flow model, substitute and complementary goods. It asks essential questions about the study and branches of economics, the roles of producers and consumers in different economic systems, the circular flow model, demand and supply, scarcity, and how scarcity influences consumer sovereignty.