Supply, demand, and price are the main elements by which the market of goods and service is led. The market of goods consists of different market structures, the most common one being the division of monopoly, monopolistic competition, and oligopoly. The imperfect competition stands for the existance of a certain number of bidders who are characterized by having the market power and the ability to influence the price of goods and service on the market by changing their output to a certain extent. It is most common for the monopoly to be explained as a market situation where there is only one enterprise that constitutes the entire branch or a sector. The distinctive feature of the monopoly is the ability of a monopolyst to change the price without the fear of losing its buyers. One can distinguish between the natural and legal monopoly. Oligopoly is a structure that implies the existance of a small number of certain goods manufacturers, each of whom has a significant part in the total market supply. The oligopolistic market simply the productes that can, but do not have to, be differentiated, as long as the majority, or the whole production, is distributed between the couple of competitors. The monopolistic competition appears on the market where a huge number of manufacturers produces the similar, but not identical goods, meaning that there is a differentiation of products that leads to the market power. Given that the access to the market is free, unlike the oligopolistic, the new competitors will enter the branch if they believe to be able to achieve economical profit.