Query what you need. Get exactly that.
With GraphQL, the client makes declarative queries, asking for the exact data needed, and in exactly what was asked for is given in response, nothing more. This allows the client have control over their application, and allows the GraphQL server to perform more efficiently by only fetching the resources requested.
Fetch many resources in a single request.
GraphQL queries allow access to multiple root resources, and also smoothly follow references between connected resources. While typical a REST API would require round-trip requests to many endpoints, GraphQL APIs can get all the data your app needs in a single request. Apps using GraphQL can be quick even on slow mobile network connections.