Map services and feature services are made up of layers. These layers group together geographic features with the same geometry type and the same sets of properties. Layers are referred to by their numerical index in the list. The layer index starts at 0 for the bottom layer, and goes up one for each additional layer. The URL might look something like this for the first layer in a map service:

http://<GIS-web- server>/arcgis/rest/services/<folder>/<mapname>/MapServer/0

Map layers offer a whole host of data to help you understand what you're viewing. The layer's name property comes either from its name in the .mxd file, or from the layer in the Table of contents, if the file is unsaved. The map layer also provides a description, and copyright data. The display field property tells the map service what to use when labeling features, if labeling is turned on.

Map layers also provide important data that you can use in your application. The type parameter tells you...