JSON Server is a tool that allows frontend developers to quickly create a mock REST API using a simple JSON file to define endpoints and sample data, making it particularly useful when backend routes are not yet complete. It enables the execution of standard HTTP requests like GET, POST, and PUT, as well as more advanced operations such as filtering, sorting, and searching data. The server can be initiated by watching a db.json configuration file, and it supports both plural and singular endpoints, allowing for the creation of data relationships using identifiers. JSON Server also offers additional features like database snapshotting, custom route aliases, port changes, and custom middleware, providing flexibility and customization for various development needs. This makes it an ideal solution for quickly setting up a fake API to validate frontend components, with the ability to further extend functionality through middleware and custom configurations.