City Xplorer -Special Map That Supports Public Transport (Enhanced Pedestrian mode) - Suitable for Walking - BUS - Train (When you visit a City as a Tourist)
City Navigator - General purpose Map for Driving - Cycling - and Walking (No Enhanced Pedestrian Mode) (Doe's Not Support Public Transport)
StreetMaps - Same as City Navigator - Garmap used the Name Streetmaps in South Africa.
TOPO Topographical maps have elevation contours in the Map can be combined with Recreational MAPS for Hiking, Cycling, Adventure. Sometimes called TOPO & REC
Bluechart is for Navigating the OCEAN by Ship or Boat or Yacht (I wish!!).
Garmin maps are vector-based ,and in few cases raster-based, and stored in the built-in memory or loaded from additional flash media. There is a 'basemap' too that displays all country borders and major cities.
Garmin offers a wide variety of maps for purchase, including detailed:
"On the road maps" (CityNavigators):
Detailed road maps and points of interest for Garmin GPS device, so you can navigate with exact, turn-by-turn directions to any address or intersection.
"On the Trail Maps" (Topographic maps):
provides detailed topography including terrain contours, elevations, geographical points — even 3-D terrain shading on compatible devices. All TOPO series maps include the following features:
interstates, state highways, local roads and trails
lakes, rivers, coastline, perennial and annual streams
national parks, forests and/or conservation areas
points of interest such as campgrounds and scenic lookouts
"On the Water Maps" (nautical Bluecharts)
These charts provide tidal stations, currents, depth contours, IALA symbols and included fishing charts,
BlueChart g2 also adds Safety Shading which allows the user to enable contour shading for all depth contours shallower than the user-defined safe depth.