Fast food is the term given to food that can be prepared and served very quickly. While any meal with low preparation time can be considered to be fast food, typically the term refers to food sold in a restaurant or store with low quality preparation and served to the customer in a packaged form for take-out/take-away.
The capital requirements involved in opening up a fast food restaurant are relatively low. Restaurants with much higher sit-in ratios, where customers tend to sit and have their orders brought to them in a seemingly more upscale atmosphere, may be known in some areas as fast casual restaurants.
Many petrol/gas stations have convenience stores which sell pre-packaged sandwiches, doughnuts, and hot food. Many gas stations in the United States also sell frozen foods and have microwaves on the premises in which to prepare them.
Modern commercial fast food is often highly processed and prepared in an industrial fashion, i.e., on a large scale with standard ingredients and standardized cooking and production methods. It is usually rapidly served in cartons or bags or in a plastic wrapping, in a fashion which minimizes cost.