The authors analyze imperfect competitive markets with specific consumers' preferences. The companies compete there not only with prices but also with product characteristics. The authors analyze horizontally differentiated goods. The presentation concerns markets on which consumers choose their optimal characteristics of a product (love of characteristics). Such preferences are analyzed in the location theory of Hotelling (1929) and approaches of Lancaster (1979, 1980) and Salop (1979). Depending upon a number of companies constituting an industry such markets are treated in microeconomic theory as an oligopoly or a monopolistic competition. The authors usually present a model with 2 companies as a simplification of a model of an industry with n firms. The authors reject this simple presentation only when look for a number of firms in the industry in the equilibrium state.