A supermarket is a self-service store offering a wide variety of food and household merchandise, organized into departments. It is larger in size and has a wider selection than a traditional grocery store and it is smaller than a hypermarket or superstore.

The supermarket typically comprises meat, fresh produce, dairy, and baked goods departments along with shelf space reserved for canned and packaged goods as well as for various nonfood items such as household cleaners, pharmacy products, and pet supplies. Most supermarkets also sell a variety of other household products that are consumed regularly, such as alcohol (where permitted), household cleaning products, medicine, clothes, and some sell a much wider range of nonfood products.

The traditional suburban supermarket occupies a large amount of floor space, usually on a single level, and is situated near a residential area in order to be convenient to consumers. Its basic appeal is the availability of a broad selection of goods under a single roof at relatively low prices. Other advantages include ease of parking and, frequently, the convenience of shopping hours that extend far into the evening or even 24 hours a day. Supermarkets usually make massive outlays of newspaper and other advertising and often present elaborate in-store displays of products. The stores often are part of a corporate chain that owns or controls (sometimes by franchise) other supermarkets located nearby — even transnationally — thus increasing opportunities for economies of scale.

In North America, supermarkets typically are supplied by the distribution centers of its parent company, such as Loblaw Companies in Canada, which operates thousands of supermarkets across the nation. Loblaw operates a distribution center in every province — usually in the largest city in the province.

Supermarkets usually offer products at low prices by reducing their economic margins. Certain products (typically staple foods such as bread, milk and sugar) are occasionally sold as loss leaders, that is, with negative profit margins. To maintain a profit, supermarkets attempt to make up for the lower margins by a higher overall volume of sales, and with the sale of higher-margin items. Customers usually shop by placing their selected merchandise into shopping carts (trolleys) or baskets (self-service) and pay for the merchandise at the check-out. At present, many supermarket chains are attempting to further reduce labor costs by shifting to self-service check-out machines, where a single employee can oversee a group of four or five machines at once, assisting multiple customers at a time.