Map image layers
Map image layers are collections of map cartography organized by location and scale. These layers can include both features and imagery, and they can be displayed dynamically or as cached image tiles.
The source of a map image layer is a map service, so the feature layers contained in the service may be identifiable in a web map. However, if raster data is included in the map image layer, pixel value and band information is not available in the map image layer. You cannot perform raster analysis with a map image layer. Raster or imagery data in a map image layer operates much like a tile cache. As you browse the map, new map images are generated and displayed.
Map image layers can be dynamically displayed over basemaps that use a different coordinate system. For map image layers displayed as cached image tiles, the tiling schema must match that of the map's basemap or the map image layer must be used as the basemap.