Imagine being in a sailing boat in the Southern Ocean, 3000 miles from the nearest land and wanting to know which way to go. The GPS will tell you where you are and which way you need to go to reach your objective, and many other things depending on the model.
I have a Garmin Etrex that I use as a "receiver" this recognises anything up to 12 satellites at a time and works out where I am on the globe. The clever bit is that I connect the GPS to my laptop, this has Geo-referenced maps of the country that I'm in, and the GPS locates my position and shows it on the map. For all intents and purposes the map is just a "picture" of where I am, be it land or sea, and my position within the picture. As I move along the GPS will "track" my movement and I can determine whether or not I'm travelling in the right direction. Yes I also have road maps of Europe, and I do use the GPS with them too, and in the UK. In fact only yesterday I had to go to and address in Taunton, I looked it up at home and pin-pointed it on Microsoft Autoroute, and put the laptop in the car. Arrived in Taunton, had a coffee, plugged in the GPS and switched on the laptop. Two minutes later I could see where I was and where I needed to go. I didn't have to find the road that I was on, on a road map, the GPS did that for me, all I had to do was follow the "green line", created earlier, and in five minutes I had arrived at my destination.
Navigating is a skill, creating waypoints, plotting, dead reckoning and watching the stars, as well as working out your position by taking bearings, however, many people don't have those skills and don't want to learn them. The GPS removes the guess work.
Just bear in mind, all electronics can fail!
My two penny's worth,
Kevin

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