All GPS interactions fall under the label Location Services or Map Kit in iOS. Must link to the CoreLocation or MapKit frameworks and import relevant headers (see advanced topics).
Maps can provide rudimentary location updates as well as showing a map, obviously. CoreLocation allows geolocation without needing a map to be present.
Maps center around MKMapView. CoreLocation centers around CLLocationManager
Requires a controller to be assigned as a delegate. Once one of the above is instantiated, it calls the delegate method