https://restfulapi.net/

What is an API ?

API is the acronym for Application Programming Interface, which is a software intermediary that allows two applications to talk to each other. Each time you use an app like Facebook, send an instant message, or check the weather on your phone, you’re using an API.

When you use an application on your mobile phone, the application connects to the Internet and sends data to a server. The server then retrieves that data, interprets it, performs actions and sends it back to your phone. The application then interprets that data and presents you with the information you wanted in a readable way.

The API is the interface that can be asked by a service to get information from the database.

Your phone’s data is never fully exposed to the server, and likewise the server is never fully exposed to your phone. Instead, each communicates with small packets of data, sharing only that which is necessary.

Modern APIs adhere to standards (typically HTTP and REST), that are developer-friendly, easily accessible and understood broadly.

What is REST ?

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.

REST is a set of architectural constraints, not a protocol or a standard. In order for an API to be considered RESTful, it has to conform to these criteria:

• Uniform interface :
  • Identification of resources – The interface must uniquely identify each resource involved in the interaction between the client and the server.
  • Manipulation of resources through representations – The resources should have uniform representations in the server response. API consumers should use these representations to modify the resources state in the server.
  • Self-descriptive messages – Each resource representation should carry enough information to describe how to process the message. It should also provide information of the additional actions that the client can perform on the resource.
  • Hypermedia as the engine of application state – The client should have only the initial URI of the application. The client application should dynamically drive all other resources and interactions with the use of hyperlinks.
• Client-server that separates the user interface concerns (client) from the data storage concerns (server).
• Stateless mandates that each request from the client to the server must contain all of the information necessary to understand and complete the request.
• Cacheable: a response should implicitly or explicitly label itself as cacheable or non-cacheable. If the response is cacheable, the client application gets the right to reuse the response data later for equivalent requests and a specified period.
• Layered system style allows an architecture to be composed of hierarchical layers by constraining component behavior. For example, in a layered system, each component cannot see beyond the immediate layer they are interacting with.
• Code-on-demand (optional): downloading and executing code in the form of applets or scripts.