PostGIS is an extension for the PostgreSQL object-relational database that enables the storage of geographic objects. PostGIS is designed according to the OpenGIS Simple Feature Access for SQL specification published by the Open Geospatial Consortium.
The current stable version is PostGIS 2.0.3 (released March 1st, 2013) which adds in raster support, more advanced 3D support, topology, and tiger geocoder.
The latest development version is PostGIS 2.1.0 (not yet released) which adds improved speed for geography and raster, more functions, speed and stability for raster and topology, upgraded tiger geocoder for tiger 2012 census and ability to install tiger geocoder using CREATE EXTENSION.
PostGIS has been developed by Refractions Research and others and is released under the GNU General Public License.