Relay is built by Facebook and integrates deeply with GraphQL, a query language for APIs that allows clients to request exactly the data they need. Unlike traditional REST APIs, where clients request data from predefined endpoints, GraphQL lets clients specify the structure of the response, enabling more flexible and efficient data interactions. Relay takes this concept further by providing developers with a sophisticated layer to handle data fetching, state management, and caching automatically.

    Relay operates by connecting React components to GraphQL queries and automatically handling the communication with the backend. This is achieved through a high-level abstraction, which significantly reduces the amount of boilerplate code developers need to write for fetching data.