JSON-RPC is a remote procedure call (RPC) protocol that uses JSON (JavaScript Object Notation) as its data format. It allows clients to send requests to a server and receive responses in a structured way. This makes it easy for different systems to communicate over a network, as JSON is lightweight and easy to parse. The protocol defines a simple way to call methods on a server, passing parameters and receiving results. It supports both synchronous and asynchronous calls, making it flexible for various applications. JSON-RPC is often used in web services and APIs to facilitate communication between clients and servers.