Assisted Global Positioning System (A-GPS) assists the mobile device in finding satellites. A-GPS speeds up the location calculation remarkably and makes your GPS functionality start-up faster.
When using A-GPS, the device receives useful satellite information from an assistance data server over the cellular network. With the assisted data the device can detect the set of satellites that are worth listening to, that is, the satellites that are on the same side of the planet with your device. Without the assisted data the device should listen to all satellites and getting a GPS fix would take a longer time.
A-GPS is a network service and it is used by default in Nokia devices that support A-GPS.
A-GPS is available in all countries and does not depend on specific operator services.