Fast food is food cooked in bulk and in advance and kept warm, or reheated to order. Many fast-food restaurants are part of restaurant chains or franchise operations, and standardized foodstuffs are shipped to each restaurant from central locations. There are also simpler fast-food outlets, such as stands or kiosks, which may or may not provide shelter or chairs for customers. Because the capital requirements to start a fast-food restaurant are relatively small, particularly in areas with non-existent or poorly enforced health codes, small individually-owned fast-food restaurants have become common throughout the world. Restaurants such as Culver's and Noodles, where the customers sit down and have their food orders brought to them, are also considered fast food.

Fast-food outlets are take-away or take-out providers, often with a "drive-thru" service which allows customers to order and pick up food from their cars; but most also have a seating area in which customers can eat the food on the premises.

Nearly from its inception, fast food has been designed to be eaten "on the go" and often does not require traditional cutlery and is eaten as a finger food. Common menu items at fast food outlets include fish and chips, sandwiches, pitas, hamburgers, fried chicken, french fries, chicken nuggets, tacos, pizza, and ice cream, although many fast-food restaurants offer "slower" foods like chili, mashed potatoes, and salads.

"Fast food" is also available in other places. For example many petrol/gas stations have convenience stores which sell pre-packed sandwiches, donuts or hot food. Supermarkets often include their own cafes with prepared food service counters. Some, like ASDA and Wal-Mart may even include a well-known fast food chain within their own store, such as McDonald's.