If you go to Settings > Privacy > Location Services, you can toggle Location Services being on and off. If you turn LS off, everything that uses your GPS location won't be able to fully function. It ranges from small things, like Snapchat's filter options not being available to you, to large things, like Maps not being able to use GPS location. Which is why Find My iPhone will not function if you turn LS off completely.
However, you can manage which applications use your location and which do not. Since I am often on the go, and don't want apps like Twitter or Facebook to post my location, I have it set to "Never" for whether or not I allow those apps to access LS. But for apps like Maps and Find My iPhone, I have it set to allow them to access LS and use my location. If you don't do that, you won't be able to use Maps, Find My iPhone, or any app that utilizes the LS function.