What is GPX data?
GPX is an XML file format for GPS data, as explained by Wikipedia:
It can be used to describe waypoints, tracks, and routes. The format is open and can be used without the need to pay licence fees. Its tags store location, elevation, and time and can in this way be used to interchange data between GPS devices and software packages. Such computer programs allow you for example to view your track, project your track on satellite images (in Google Earth), annotate maps, and tag photographs with the geolocation in the Exif metadata. [...] In GPX, a collection of points, with no sequential relationship (the county towns of England, say, or all Skyscrapers in New York), is deemed a collection of individual waypoints. An ordered collection of points may be expressed as a track or a route. Conceptually, tracks are a record of where a person has been, routes are suggestions about where they might go in the future.