Garmin POI BMP
Garmin POI CSV
Garmin POI GPX
Garmin POI (Custom POI with extended info)
Garmin MP3 (Audio alert for Garmin POI file)
Garmin upload (direct)
Garmin GPX (proximity alert, phone dial, etc.)
I have read there are three files for the picture and voice; but then I also read somewhere (can't find it anymore) that the GPX file does all three. I appreciate the guidance.
You need do download at least BMP and CSV files for Garmin.
Add MP3 sounds if you want.
Use GPX files for some added features (POI display, direct phone dial, proximity alerts).
The only way to explore what your Nuvi can do is to TRY THEM ALL.