Layers and maps in ArcGIS Online are exposed through the Web using a communication standard known as Representational State Transfer (REST). These web services are commonly referred to as REST Services. REST is a lightweight communication format between the producer and the consumer, which makes it extremely popular among cloud-based Application Programming Interfaces, or APIs, such as the one produced by ESRI. When a producer exposes their web services using the REST architecture, they are called RESTful APIs or a REST API. In our case, we refer to the maps and layers exposed through ArcGIS Online using REST as the ArcGIS REST API.
With the ArcGIS REST API, you can perform multiple queries, share data within your organization, expose data from your organization to the public, and configure parts of your internal ArcGIS infrastructure, such as ArcGIS...