Blue Eagle is essentially correct. But as this one has come up before it might as well be clarified here and now.
The IFS/CIC/ISD (delete as required) inputs Flight Number / Departure Point / Destination / Gross Flight Time / GMT variation at Destination - from the cabin computer.
The Moving Map then picks up data from the FMC/Flight Data bus as follows :
Take Off Time
Distance to Go
Altitude
Wind
AirSpeed
GroundSpeed
Aircraft Heading/Track
Current Lat/Long
ETA
All these are selectively converted to metric values (or whatever) as defined by a selectable customer option.
From all these the Display software just displays what it gets from the FMC. Thus you will often see the ETA change as winds change / crew input data is absorbed etc.
The aircraft symbol is aligned to represent heading/track and position from the FMC.
However - as correctly mentioned previously. This system does sometimes have a mind of its' own and can be confusing. It is just a piece of Disneyworld by and bye. It is a clever piece of software and is improving all the time. There are many versions out there - even on the same airplanes/companies. Some are better than others. It sure beats sending back the little maps with the position and flight data on; to be passed around as in the distant past.
MG