A REST Client is a software tool or library that allows users to interact with web services that follow the REST (Representational State Transfer) architectural style. It enables developers to send requests to a server and receive responses, typically using standard HTTP methods like GET, POST, PUT, and DELETE. This interaction is essential for accessing and manipulating resources over the internet. REST Clients can be used in various programming languages and environments, making them versatile for different applications. Popular examples include tools like Postman and libraries such as Axios for JavaScript. These clients simplify the process of testing and integrating APIs, enhancing development efficiency.