It is just assisted GPS, it allows you to find you position much easier as it can either download a satelite almanac so that it finds the satelites quicker, or it can work out it's position initally while waiting for a true GPS fix from cell information.
For instance, google maps running on my nokia initially says "position accurate to 2000m" at first, but once it gets a GPS fix it revises it town to 20 feet or some such.
Some systems allow offloading of fragmented GPS signal to an assistance server which has much more porcessing power and knows its exact position.
Some systems do rely on having the back end connection to work. I expect these have GPS receivers, but no ability to work out their position.