The document discusses different market structures including perfect competition, monopoly, monopolistic competition, oligopoly, and duopoly. It provides characteristics and diagrams to analyze each structure. A monopolistic market is described as having many firms differentiating similar products, with relatively easy entry and exit into the industry and imperfect consumer and producer knowledge. Firms in monopolistic competition can earn abnormal profits in the short run but normal profits in the long run as entry of new firms causes prices to fall.