A RESTful API (Representational State Transfer Application Programming Interface) is a set of standards and guidelines used to develop and interact with web services. RESTful APIs allow different applications or services to communicate over HTTP using simple, predictable requests. REST, a popular architectural style for APIs, leverages standard HTTP methods—GET, POST, PUT, DELETE—to retrieve, create, update, and delete resources, making it highly accessible for developers and scalable for large applications.

Key principles of RESTful APIs include:

Statelessness: Each API request from the client contains all information necessary to process the request, with no stored client context on the server. This stateless design simplifies scaling and ensures that requests can be managed independently.
Resource-Based Structure: Resources, typically objects like "users" or "orders," are represented by unique URLs, making them accessible and allowing clients to interact with them in an organized manner.
Uniform Interface: RESTful APIs maintain a consistent interface, allowing clients to interact in a predictable way, which enhances usability and reduces learning curves for developers.
Cacheability: Responses from RESTful APIs can often be cached, improving efficiency and performance by reducing redundant server requests.
RESTful APIs are widely adopted for web and mobile application development due to their flexibility, ease of use, and adaptability to different technology stacks. They allow different applications to interact seamlessly, enabling functionalities like retrieving social media posts, processing online transactions, or integrating third-party services.