This document defines key economic concepts and compares different economic systems. It begins by defining economics as the study of how scarce resources are used to meet wants and needs. An economic system is defined as how a society addresses basic questions of what, how, and for whom to produce goods and services. The main types of economic systems discussed are traditional, market, command, and mixed. Their key characteristics and advantages/disadvantages are summarized. Traditional systems rely on customs, while command systems involve central government planning and market systems use supply and demand. Mixed systems blend public and private aspects.