Map notes are a way of using a feature collection to add markup to a map. The client application provides users with drawing and attribute editing tools for the map notes.
This example uses map notes to show a neighborhood, a restaurant, and a walking route between them. These map notes were created with the ArcGIS.com map viewer.
Each piece of markup is stored using X/Y coordinate geometry, even if it's nongeographic in nature (such as an arrow polygon). Templates within the web map JSON define the types of features that can be created.