A query language for your API

GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools.Homepage http://graphql.org

Ask for what you need,
get exactly that

Send a GraphQL query to your API and get exactly what you need, nothing more and nothing less. GraphQL queries always return predictable results. Apps using GraphQL are fast and stable because they control the data they get, not the server.
GraphQL xây dựng một ngôn ngữ chung để giao tiếp với API mà nó sẽ gửi lên những field mà Client muốn và Server sẽ xem qua và trả lại chính xác những gì Client yêu cầu.

you always get back what you expect, and the server knows exactly what fields the client is asking for.