geocoding

 Geocoding  is the process of turning a text form location (such as an address or name of a place) into a set of geographical coordinates. The inverse, reverse geocoding, turns a set of geographical coordinates into an address or a place name. Either method, or both, might be used for location aware applications, or during the process of computing locations for checkins.

IndieWeb Examples

 * geotags all his posts to display the city name of where the post was created. The geocoding is done via Atlas

Geocoding Services

 * Nominatim uses OpenStreetMap data
 * Google Maps Geocoding API
 * Mapbox
 * Geocoder (U.S. Census Bureau)
 * Esri's mapping services
 * http://www.geonames.org/ - not strictly a geocoding service, but has free databases/webservices for countries, postal codes, placenames, and their coordinates.