Business directory services provide lists of businesses in a given area and matching a specified name or category.

Business directory data comes from third-party providers of such data. These providers probably have different business categories, and even different hierarchical structures. A unifying pattern in the various approaches is that businesses are categorized by subject and location. The location component is well understood; for example, for the United States, either a ZIP code or the combination of a city and state, and optionally a specific address, can be used to determine the location from which to start searching.

The categorization of businesses, on the other hand, is not uniformly implemented. Some providers offer a flat list of categories, user-selected by simple substring matching. Others offer a 3-level or 4-level hierarchical organization of subcategories, often with a fanout (maximum number of child categories at a level) of 20 to 50, and sometimes more than 100. A user might start the hierarchy traversal at the root of the hierarchy (by default). Alternatively, a user might enter a keyword that is matched to an appropriate starting point within the hierarchy. Such keyword matching might go beyond simple substring matching and result in more intelligent choices.