We covered a lot of ground in this chapter. We tried to identify the process by which data is added to the map. We identified the data source, such as ArcGIS Server service, OGC data, CSV, KML, and so on. Then, we covered the API provided modules that support the display of, and further operations on, three major ArcGIS REST service data sources, namely the ArcGIS Tiledmap service layer, the ArcGIS DynamicMapService layer, and the feature layer. You also learned how to instantiate the layers and how to navigate their properties and events. We also dealt with a special kind of layer namely graphics layer, which is the top-most layer in the map and is used as a container object for all the graphics in the map. We got a taste of the plethora of in-built widgets provided by Esri. In the next chapter, we will have an in-depth look into writing spatial queries and retrieving the results. You will also learn how to use geometry services and the geometry engine to process geometric operations.