Three major features of Graphql:
1. First, it is declarative . The result format of the query is determined by the requester (ie the client) rather than the responder (ie the server), that is to say, the return of a GraphQL query result is the same as the structure of the client request, no more, no less, Neither increase nor decrease.
2. Second, it is composable . A GraphQL query structure is a hierarchical set of fields, which can be nested or combined at any level, that is to say, it can meet the requirements by combining and nesting fields
3. Third, it is strongly typed . Strong typing guarantees that only if a GraphQL query satisfies the set query type, the result of the query will be executed.