The place where supply and demand meet is called the market. One of the markets is the goods market which is divided into perfect and imperfect competition. Monopoly, monopolistic competition and oligopoly are a part of imperfect competition. The difference between all structures is the number of sellers on the market. Perfect competition has a large number of sellers who cannot control the price of their product, monopoly has one seller who creates the price, monopolistic competition consists of a large number of sellers who can influence the price slightly, and oligopoly represents a small number of large sellers who can relatively influence the price of the products they offer. Of all the structures, perfect competition is the only example that is only considered possible in theory. Monopoly produces goods that do not have a close substitute. Two types of monopoly are natural and legal monopoly. It is extremely difficult to enter the monopolistic branch because it is protected from the competition. Perfect competition and monopolistic competitions are two similar structures, but they differ by product differentiation. Perfect competition produces homogeneous products, and monopolistic competition differentiated. In the long term, economic profits reach zero for monopolistic competitors. Oligopoly offers limited choice to customers as it has between 2 and 15 sellers. Sellers in oligopoly must always think about their competitors’ moves. For oligopoly, the product can be either homogeneous or differentiated, and the barriers to entry can either be natural or artificial. A situation in which there are only two sellers is called a duopoly and it represents the simplest form of oligopoly. An example of an oligopoly in the Republic of Croatia is visible in a mobile communication network. There are three main sellers: Croatian Telecom, A1 Croatia and Telemach. Unlike the mobile telecommunications network, Hrvatske vode are an example of a monopoly. They act according to the law and supply water to Croats and take care of the usage, irrigation and water protection, as well as money charges. Monopolistic competition is presented through the coffee market, which consists of a large number of sellers. Some of the sellers are Starbucks, Illy, Nespresso etc. The differentiation of coffee arises through different processing methods, places of origin, strength, or quality.