What is REST used for?

REST (Representational State Transfer) is an architectural style for building distributed systems, particularly web services. It defines a set of constraints and principles that help create scalable, fault-tolerant, and easily maintainable web services.

Main principles of REST:

Client-server architecture: Separation of concerns between the client and the server. The client requests resources, and the server responds to requests.
Stateless: The server does not store information about the client's state between requests. Each request must contain all the information needed for processing.
Caching: Clients or intermediate nodes can cache server responses.
Uniform Interface: Simplifies interaction between client and server through standardized ways of accessing resources:
- Identification of resources via URI.
- Manipulation of resources through representations (e.g., JSON or XML format).
- Self-descriptive messages.
- HATEOAS (Hypermedia as the Engine of Application State): Resource representations contain links to other related resources.
Layered System: The system can consist of multiple layers (e.g., load balancer, cache, server), each of which does not affect the interaction between client and server.
Code on Demand (optional): The server can transmit executable code to the client (e.g., JavaScript), which extends the client's functionality.

Purpose of REST:

Simplify integration: Provides a standard way for different systems to interact.
Scalability: Lack of server state simplifies horizontal scaling.
Performance: Caching reduces server load and response time.
Reliability: Layer separation increases fault tolerance.
Portability: Clients can interact with different servers implementing RESTful APIs.

REST is used to create web APIs that allow applications (websites, mobile apps, other services) to interact with each other and access data and functionality.