Sure. So when you're in cell phone range and have a new destination in mind, you just enter the place name or address - or select a spot on the map. Or even select the destination with your voice. Hit the "directions" button and you'll get a layout of the route and optional routes along with driving time and ETA. Then hit "start" and voila! it starts telling you where to turn. Reroutes you around traffic, shows where the road is backed up, keeps your ETA updated as you go, etc. etc. You don't need constant cell service as you go. Once you select your destination and start navigation it downloads a map of your entire route and the surrounding areas so you're set even if you're driving in and out of coverage areas. The phone's GPS is completely independent and can always find it's location on the map (unless you're underground).
If you're going to be out in the sticks changing destinations then you'll want to download maps in advance which is pretty simple. For example, last spring I was in the French Alps and wasn't sure what coverage with my American phone was like so I downloaded an area a couple hundred miles on a side just in case. In the event it was unnecessary - the French cell network is great. Here's map download instructions. This is iPhone/iPad specific but Android is almost exactly the same. edit: oh, there are Android instructions at the link - I just didn't see the button.
https://support.google.com/maps/answer/6291838?co=GENIE.Platform=iOS&hl=en
I've never seen a system that could match Google for turn-by-turn directions and traffic rerouting. Maps are always up to date (if you download they update themselves when needed), traffic rerouting is fantastic and gives you plenty of warning for turns and even for roundabouts gives you a little diagram and tells you which exit to take out of the circle. I use it constantly in the US and have also used it to navigate in Singapore, London and all over north-western Europe.
If you have a cell phone you already have the system (maybe on an iPhone you have to download it for free - Google's app is way better than Apple's) so you might as well give it a trial run before you decide on anything. My 83 year old mother and my 16 year old son both use it - you can too!