API

A REST API (also known as RESTful API) is an Application Programming Interface that conforms to the constraints of REST architectural style and allows for interaction with RESTful web services. REST stands for REpresentational State Transfer and was created by Roy Fielding in 2000 who also co-founded the Apache HTTP Server project and has been heavily involved in the development of HTML.

An API helps you communicate with a system so it can understand and fulfill the request.

You can think of an API as a mediator between the users or clients and the resources or web services they want to get. It’s also a way for an organization to share resources and information while maintaining security, control, and authentication—determining who gets access to what.

The Open API Initiative was created to standardize REST API descriptions across vendors. As part of this initiative, the Swagger 2.0 specification was renamed the OpenAPI Specification (OAS) and brought under the Open API Initiative.

The OpenAPI Specification comes with a set of opinionated guidelines on how a REST API should be designed. That has advantages for interoperability, but requires more care when designing your API to conform to the specification.

OpenAPI promotes a contract-first approach, rather than an implementation-first approach. Contract-first means you design the API contract (the interface) first and then write code that implements the contract.

Tools like Swagger can generate client libraries or documentation from API contracts.

(read more about Open API specifications)[https://oai.github.io/Documentation/specification.html]