What is GPX?
GPX stands for GPS Exchange Format. It allows people to exchange data about:
Geocachers use GPX files to download cache coordinates into their GPS receiver.
This saves the hassle of entering coordinates of each cache into their GPS receiver.
The normal process it to download waypoints from a cache listing website into waypoint management software on your PC, and then download the waypoints into your GPS.
GPX was developed by Topografix, which publishes the GPX format specfication.
Different GPX formats
GPX defines the method of storing waypoints, but it doesn't define the method of storing the additional information you need to store for a cache, for example it's terrain and difficulty.
Groundspeak developed extensions to cover this information, however unfortunately they have made the extensions proprietary so they cannot be used by other cache listing websites. [Geocaching.com] makes their GPX files available to Premium Members via a method called Pocket Queries.
Geocaching Australia has therefore needed to develop its own GPX extensions.
These are incompatible with the Groundspeak extensions, however they are non-proprietary.
The Geocaching Australia extensions are being supported by new software.
The current status is listed under waypoint management software.