Its actually
Global
Positioning
System, and because you can get altitude information from GPS these days, its not specifically for the ground. This term is actually being replaced by GNSS (Global Navigation Satellite System), which will use the American GPS system and the European GLONASS system in conjunction

If you are using FS9 & FSX, then if you go to the ATC window and request a change of destination then you will create a new .pln file, but still using you present position. However if you are not using the ATC with FS9 & FSX then you will just have to use the Direct to button and select each waypoint as it come up. This is not possible in FS8. Hope this helps.