What is REST?  Representational State Transfer (REST) is usually defined as a software architecture style that applies some constraints to a web service. It identifies a set of resource-centric rules that describe the roles and the interaction between the constraints of a distributed hypermedia system, instead of focusing on the implementation of the components. Although it is quite rare to find a REST service that does not use HTTP, the definition does not mention any of these topics and instead describes REST as media- and protocol-agnostic.

The preceding definition can be further explained with an example. Consider an e-commerce website. When you browse a list of products and click on one them, the browser interprets your click as a request to a specific resource; in this case, the details of the product you clicked on. The browser makes an HTTP call to the URI, which corresponds to the details of the product and asks for a specific resource using the URI. This process is shown in the following diagram:

The concept of REST is pretty similar: the client asks the server for a specific resource, and this allows them to navigate and obtain other information about resources stored on the server.