GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data.
The advantage of GraphQL over REST API is that it is strongly-typed which allows API consumers to know exactly what data is available, and in what form it exists. According to the docs: “Every GraphQL service defines a set of types which completely describe the set of possible data you can query on that service. Then, when queries come in, they are validated and executed against that schema.”
The benefit for the end-user is that it enables querying many resources and retrieving the exact data  he/she wants in one request.
Users now has ability get data they need, also they can easily explore data by key filters.

For instance user wants to get organizations, owned plants and main systems in one request.