This book investigates the essence of economic activity and the form of its display in conditions of natural, market and regulated economy. The dialectic and teleological analysis of economic activity allows the authors to reveal the reflective relations between such fundamental economic categories such as, production and consumption, supply and demand, product and resource, cost and utility, profit and saving, expansion and recession, etc. The revealing of the interdependence between specified categories allows the authors to understand more deeply the essence of economic processes, logic of formation of business cycles, and to create adequate model of economy. This book is intended for lecturers and students of economic profile, as well as experts interested in problems of economic theory.