REST APIs are designed to make it easy for applications to interact with each other by exchanging data and functionalities in a secure and standardized way using HTTP requests. They rely on a stateless, client-server, cacheable communications protocol and use standard HTTP methods such as GET, POST, PUT, and DELETE to perform CRUD operations. REST APIs play a crucial role in modern application architecture, especially for IoT and microservices, enabling communication between devices and services. The key principles of REST include simplicity, scalability, and interoperability, making it a popular choice for building web and mobile applications. Emerging trends like HTTP/2 and serverless computing are also shaping the landscape of REST APIs, offering improvements in performance and scalability. While other protocols like GraphQL and gRPC offer specialized solutions for specific projects, REST remains a smart choice for building flexible and interoperable web and mobile applications.