Retailing is the sale of goods and services to ultimate consumers for personal, nonbusiness use. Any institution (even a manufacturer) may engage in retailing, but a firm engaged primarily in retailing is called a retailer. Retailers serve as purchasing agents for consumers and as sales specialists for producers and wholesaling middlemen. They perform many specific activities, such as anticipating customers' wants, developing product assortments, and financing.

There are about 1.1 million retail firms in the U.S. ; collectively they generated almost $3.5 trillion in sales during 2004. Most retail firms are small—either single stores or several stores under common ownership. Small retailers can survive, and even prosper, if they remain flexible and pay careful attention to personally serving customers' needs. Retailers' profits are usually a tiny fraction of sales, generally about 3%.

Besides making decisions about product, price, promotion, and customer services, retailers also must devise strategies related to physical facilities. Specific decisions concern location, size, design, and layout of the store. Downtown shopping areas declined as suburban shopping centers grew. Now regional shopping centers are feeling competitive pressures from many sources, including Internet firms.

Retailers can be classified by (1) form of ownership, including corporate chain, independent store, and various kinds of contractual vertical marketing systems (notably franchising), and (2) key marketing strategies. Types of retailers, distinguished according to product assortment, price levels, and customer service levels, include department stores, discount stores, limited-line stores (notably specialty stores, off-price retailers, and category-killer stores), supermarkets, convenience stores, and warehouse clubs. Mature institutions such as department stores and supermarkets face strong challenges from new competitors, particularly discount chains, category-killer stores in various product categories, and online retailers.

Although the large majority of retail sales are made in physical stores, as much as 20% occur away from stores. And this proportion is growing steadily. Five major forms of nonstore retailing are direct selling, telemarketing, automatic vending, online retailing, and direct marketing. Each type has advantages as well as drawbacks. Online retailing, in particular, is surging dramatically.