Walk into any supermarket or scroll through an online store, and you will find shelves filled with dozens of breakfast cereals, shampoos, or phone cases—each slightly different, each trying to win you over. Most of these industries are not perfectly competitive, nor are they dominated by a single giant monopoly. This chapter explores the middle ground: monopolistic competition, where many firms sell varieties of the same basic product, and we will see why advertising, brand image, and niche positioning matter so much for profits.