The word suburb mostly refers to a residential area, either existing as part of a city or as a separate residential community within commuting distance of a city. Some suburbs have a degree of administrative autonomy, and most have lower population density than inner city neighborhoods. Suburbs first emerged on a large scale in the 19th and 20th century as a result of improved rail and road transport, leading to an increase in commuting. Suburbs tend to proliferate around cities that have an abundance of adjacent flat land.[1] Any particular suburban area is referred to as a suburb, while suburban areas on the whole are referred to as the suburbs or suburbia, with the demonym for a suburb-dweller being suburbanite. Colloquial usage sometimes shortens the term to burb.

Source: http://en.wikipedia.org/wiki/Suburb