A type of handset-based position location technology. To determine location, the phone takes readings from both GPS satellites and nearby cellular base stations (towers), with the help of a location server on the network.
The location server on the network is required to tell the phone which satellites to look for, and/or to help perform the complex calculations that provide the most precise location information.
This technology generally provides better accuracy than GPS-only and cellular-network-only technologies. A-GPS also works in places where GPS-only technologies do not work well, such as dense urban areas, inside buildings, and in moving cars.
All modern phones include A-GPS or some equivalent. In the U.S., it is required by law so that emergency personnel can locate you when you call 911, in case you cannot explain your exact location to the dispatcher.
A-GPS is a hardware feature that provides latitude and longitude coordinates to the phone's software. The software can then use this information to provide any number of location-related features, such as mapping, navigation, suggestions for things to do nearby, and geo-fencing.
All modern smartphones include mapping and navigation software.