Market structures refer to the different ways that markets are organized based on the number of firms, the type of products they sell, and how they compete. The main types include perfect competition, where many firms sell identical products; monopolistic competition, with many firms selling similar but differentiated products; oligopoly, where a few firms dominate the market; and monopoly, where a single firm controls the entire market. Understanding market structures helps us analyze how prices are set and how firms behave. For example, in a monopoly, the single firm can set higher prices due to lack of competition, while in perfect competition, prices are driven down by many sellers competing for customers.