Central Business District or CBD is the focal point of a city. It is the commercial, office, retail, and cultural center of the city and usually is the center point for transportation networks.
There are no boundaries to the CBD. The Central Business District is essentially about perception. It is usually the “postcard image” one has of a particular city. There have been various attempts at delineating the boundaries of the CBD but, for the most part, one can visually or instinctively know when the Central Business District starts and ends as it is the core and contains a plethora of tall buildings, high density, a lack of parking, transportation nodes, a large number of pedestrians on the streets and generally just a lot of activity during the daytime.
The “CBD” is the central district of a city, usually typified by a concentration of retail and commercial buildings. City center differs from downtown in that the latter can be geographically located anywhere in a city, while a city center is generally located near the geographic heart of the city.
Source: https://en.wikipedia.org/wiki/Central_business_district
