A REST API (also known as RESTful API) is an application programming interface (API or web API) that conforms to the constraints of REST architectural style and allows for interaction with RESTful web services. REST stands for representational state transfer.

An API is a set of definitions and protocols for building and integrating application software. It’s sometimes referred to as a contract between an information provider and an information user—establishing the content required from the consumer (the call) and the content required by the producer (the response).

A RESTful API uses commands to obtain resources. The state of a resource at any given timestamp is called a resource representation. A RESTful API uses existing HTTP methodologies such as:

• GET to retrieve a resource
• PUT to change the state of or update a resource, which can be an object, file or block
• POST to create that resource
• DELETE to remove it

• A client-server architecture made up of clients, servers, and resources, with requests managed through HTTP
• Stateless client-server communication, i.e no client information stored between each request and each request is separate and not connected
• A uniform interface between components so that information is transferred in a standard form