The market is the place where supply and demand meet. In the literature there are several different market structure classifications, from Stackelberg, Weintraub to Samuleson's classification of market structures. Weintraub's and Samuelson's market structure classification is more extensive than Stackelberg's classification. This graduete paper will elaborate perfect competition, monopoly, oligopoly and monopoly competition. A perfect competition is a market structure that is seldom seen in the market, and if it appears then it is on the market of agricultural products and only in some branches of agriculture. Monopoly is a market structure that appears in the market through several types. There is a legal, economic and natural monopoly. A natural monopoly occurs when an enterprise possesses a natural good and produces a unique good through them. A legal monopoly arises when the state, through its regulations and ordinance, promotes the production of a certain good. An economic monopoly arises when capital concentrates on certain parts. A oligopol is the dominant market structure in the world, especially in developed economic markets. Cournot's, Betrand's, and Edgeworth's model are classic oligopoly models that are based on the assumption that oligopolists are acting alone. In monopolistic competition there are a large number of companies whose products are not identical but are similar. So the goods that are produced in the monopoly competition are not perfect substitutes. Monopolistic competition is placed into imperfect competition.