Convert gml to gpx

What is the difference between .gml and .gpx?

Description: Geography data format created by Galdos Systems and supported by the Open Geospatial Consortium; used by geographers for storing geographical data in a standard interchangeable format.; A GPX file is a GPS data file saved in the GPS Exchange format, which is an open standard that can be freely used by GPS programs. It contains longitude and latitude location data that may include waypoints, routes, and tracks. GPX files are saved in XML format, which allows GPS data to be more easily imported and read by multiple programs and web services.