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. So, for instance, there might be timestamps for each point in a track (because someone is recording where and when they were there), but timestamps for each point in a route are unlikely to be provided, because the author is suggesting it, and nobody might ever have travelled it.

The minimum properties for a GPX file are latitude and longitude for a single waypoint. All other variables are optional.

Sample GPX Document

The following is a truncated (for brevity) GPX file produced by a hand-held GPS unit. This document does not show all functionality which can be stored in the GPX format – for example, there are no waypoints or extensions, and this is part of a track, not a route – but the purpose is to serve as a brief illustration.

GPX, or GPS eXchange Format is an XML schema designed as a common GPS data format for software applications.

It can be used to describe waypoints, tracks, and routes. The format is open and can be used without the need to pay license 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.

Source: http://en.wikipedia.org/wiki/GPS_eXchange_Format

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