PostGIS is an extension for PostgreSQL that includes geographic objects and functions. The extension implements i.a. the Simple Feature Access specification of the Open Geospatial Consortium. Although PostgreSQL already supports geometry types, these are insufficient for geographic tasks. Therefore, PostGIS creates its own data types that are better suited for geographic tasks. The following geometry types are supported:
OpenGIS with well-known text and well-known binary
Extended Well-Known Text and Extended Well-Known Binary also with height information and/or measured values
SQL/MM with Circularstring, Compoundcurve, Curvepolygon, Multicurve and Multisurface
GEOS, on the other hand, contains the numerous spatial functions and operators for geographic data.
Finally, pgRouting contains routing functions based on PostGIS.