GeoServer is an Open Source server that connects your information to the Geospatial Web.
With GeoServer you can publish and edit data using open standards. Your information is made available in a large variety of formats as maps/images or actual geospatial data. GeoServer's transactional capabilities offer robust support for shared editing. GeoServer's focus is ease of use and support for standards, in order to serve as 'glue' for the geospatial web, connecting from legacy databases to many diverse clients.
GeoServer is implemented in Java and uses GeoTools.