The iPhone provides an internal GPS that you can use to determine your current location, acquire directions to a destination or search for nearby locations of interest. Many of the iPhone's apps make use of this feature, so it is important that it works properly. You can test your GPS feature via the Maps application by viewing your location on the map and comparing it to your actual location.
Tap the Maps app on your iPhone's home screen.
Tap "Search" at the bottom of the screen.
Tap the button in the lower-left corner that looks like the top of a diagonally-pointing arrow. This centers your current location on the map, indicated by a pulsating blue dot.
Press two fingers to the map and pull them apart to zoom in on the blue dot. Read the surrounding landmarks and street names to see if the place displayed corresponds to your actual location.