This chapter contains four main parts. The first part is a general introduction to the study of economics, including the distinction between "micro" and "macro" economics, the reason for studying economics, and the usefulness of economic theory or principles. The second part introduces one of the most important ideas in economics-the concept of opportunity cost. Every choice or decision involves a cost because something always must be given up to do or purchase something else. The production possibilities schedule and curve is a part of the opportunity cost material. The third part of the chapter discusses the three economic questions faced by every society in regard to the allocation of resources and explains how these questions are answered in the private and public sectors of a market economy and by a communistic society. The last part of the chapter introduces the concepts of demand and supply. Much of what is presented in Chapters 2 through 6 expands on this material.