REST (Representational State Transfer) is an architectural style for designing networked applications based on the principles of simplicity, scalability, and statelessness. RESTful APIs (Application Programming Interfaces) use HTTP methods (GET, POST, PUT, DELETE) and uniform resource identifiers (URIs) to enable communication and data exchange between client and server applications over the internet. REST APIs are widely used for building web services, microservices, and distributed systems that follow a resource-oriented design approach.