This module is a Drupal wrapper/implementation for the Geocoder PHP library: "The most featured Geocoder library written in PHP, which helps you build geo-aware applications by providing a powerful abstraction layer for geocoding manipulations".
It is commonly used to automatically Geocode string/text Point addresses and WKT Geometries into Geofield, so as Reverse Geocode Geofield Points into String/Text Point addresses, and other Geocoder PHP library formats.