GPS works like this - Say you're a airlift rescuer. Someone is lost at sea. You could ask that person via radio or phone for their GPS coordinates. What they would do is type /gps, which will show his / her x and y coordinates, and then give you the coordinates. Once you have the coordinates, type /gpstrack [x coord. here] [y coord. here], and you will be guided there, and rescue the lost sailor.
That was one of the many uses for gps.
NOTE: You MUST buy a GPS from an electronics store before using!