[pier25]

On the server side it's very similar to REST. You define your types in a schema file, and then write functions that go fetch the data for each type. These functions are called resolvers.

For example you have a Product type, and then write the resolver function that queries the database and/or another API. When you have the data, you pass it back to the client via Apollo or Relay.

The big advantage over REST is that the client can define what data it wants and how it wants it. If you are full stack dev this isn't such a great advantage, but for bigger projects where front/back are spread among many engineers this can be an advantage. Also, since the schema defines the types, your API is almost self documented so to speak.

The big disadvantage is authentication and authorization. We kept using REST for authentication, and we couldn't find any ready made solution for role based authorization like you have in Express, Hapi, etc.

I think a combination of REST and GraphQL is the better approach.