A trade area is a user defined radius around an advertiser.

Most retail businesses have a relatively fixed area that customers come from to do business at their store In general; the trade area is either the living or work locale for the customer. The selling zone of place-based retail business will be dynamic for two reasons; the customer is moving residences or jobs or the customer is passing through on a trip that intersects the trade area. The trade area for most small businesses is 3 to 5 miles.

the geographical region in which a particular advertiser's product is sold.

The region from which a particular store(s) derives a certain percentage of its business. See Trade Area Analysis  Link:  Trade Area Analysis

The area where the entire potential customer base is found, which may extend beyond the primarily geographic market area. The trade area is defined based on a project's attributes; location and drive times; population and competition distances; and demand features.

The area surrounding your business, which provides your major customer base.

For shopping centers the geographical area from which 60-80% of a center's sales originate.

An area delineated about a central or dominant location, comprising a zone that is dependent upon production output from that location to meet internal demand, whose outermost boundaries are defined in terms of the presence or absence of interactions with that central or dominant location (for example, a localized area over which some specific activity or transaction takes place). Note that in central place theory context, the terms trade area and range are used interchangeably. Also see range.