APRS transmits your position and whatever else you put in the data stream. This could be a short text message, a short email, information about your radio, what frequency you're monitoring, etc. It needs a GPS receiver to know your position in order to transmit it. This is NOT the same thing as having a GPS with maps to tell you how to get some where.
Coverage for APRS signals varies just like repeater coverage varies. You might be hiking very near a great digipeater and have great coverage or their might not be one around and you have no coverage.
APRS operates over analog radios. Some of the Yaesu Fusion radios have APRS built in but it operates in analog mode, not in Fusion digital audio mode.
I often work where there is no cell phone coverage. I typically use a "regular" analog repeater to be able to communicate back home with my wife (she's a ham too). I do sometimes use the APRS functionality of my Yaesu FTM-400 to send text messages to her phone. This is thru the SMS gateway that some nice ham(s) created. She can even reply to me from her cell phone. Sometimes I get her replys, sometimes not. I'm told this is because some well meaning but misinformed hams have put up receive only APRS gateways. So, if my transmission goes thru one of them the reply can't follow the same path back to me. Hams need to remember that amateur radio is about two way communication and kindly take down their receive only APRS machines.