Hi..
the moving map screen you see on the A320 comes from IRU inertial reference units using inertial information (coordinates), it fine tunes itself using GPS or VOR or DME in that order, which are all independent sources of navigation, but inertial is the boss.
the bearing pointers (needles) on the screen are using VOR or NDB information only from ground stations.
If you want to fly to a VOR you can select a HDG to it using the needles or you can type it on the MCDU or FMC and the airplane will fly there using inertial reference (coordinates) with a back up from GPS, VOR or DME.
sometimes the map is wrong and you have to use the old system of VORs.
the MMR and all nav info goes to the FMGC (autopilot/ flight director) then the FMGC talks to the ELAC which moves the flight controls of the plane.
I think this is the level of understanding that you have hope it is helpfull.