This ArcGIS tool allows the user to create proximal zones based on input point features.  Any area within a zone will be more closely associated with the input point in that zone than any other input point(s).

It can be a useful tool in deciding where to place new public services within a city, e.g. a library or community health care clinic, based on where they are lacking or most needed.  The example below demonstrates current library locations along with the population they serve and their associated usage.  This information helps highlight which libraries, if any, are being either over or underutilized and therefore provide information about where new services may be needed.  The dataset table beneath the maps demonstrates that the city should consider building a new library using an available vacant lot in the Ravenswood corridor (if it is to minimize the distance to other libraries in the network).

Source: Esri.