A REST API (Representational State Transfer Application Programming Interface) is a set of rules and conventions that enables different software applications to communicate with each other over the internet. REST APIs use standard HTTP methods, such as GET, POST, PUT, and DELETE, to request and exchange data between servers and clients. This approach allows websites, mobile apps, and other digital services to interact seamlessly, regardless of the underlying technology. REST APIs are widely used because they are simple, scalable, and flexible, making it easy for developers to connect diverse systems and share information efficiently.