GraphQL is an open-source query language and runtime for APIs that was developed by Facebook. Unlike traditional REST APIs, which require multiple requests to retrieve related data, GraphQL allows developers to retrieve all the required data in a single request, resulting in improved performance and reduced network overhead. With GraphQL, developers can specify exactly what data they need, and the API will return only that data, enabling them to build more efficient and customized applications. Additionally, GraphQL provides a strongly-typed schema that makes it easier for developers to understand the structure and types of data available through the API. GraphQL has gained significant popularity in recent years and is widely used by companies of all sizes to build high-performance APIs for their applications.