Relay is a framework for building data-driven React applications that communicate with a GraphQL API. It focuses on efficiently managing the fetching, caching, and synchronization of data, while simplifying the process of integrating GraphQL into an app. Unlike traditional state management solutions, Relay is not just concerned with managing local application state but with how your app communicates with an external data source, typically a server.

    At its core, Relay leverages GraphQL's ability to request exactly the data required by a component. With Relay, developers can build declarative data dependencies, meaning that React components only need to specify the data they need, and Relay takes care of fetching it from the server and caching it for future use.