The document discusses market structure and perfect competition. It defines market structure as considering the number of firms, nature of products, degree of monopoly power, and other factors. Economists group markets into four structures: pure competition, monopolistic competition, oligopoly, and pure monopoly. The document then focuses on defining pure competition, including that it involves many small firms, standardized products, firms being price takers, and free entry and exit. It also discusses the demand, costs, revenues, and equilibrium outcomes for competitive firms.