The Relay API is meant to be used with the GraphQL client Relay.
Differences to the Simple API
The Relay API is conforming with the Relay specifications. If you don't use Relay as a GraphQL client you probably should use the Simple API. You can also use different APIs in different parts of your application.
Using the Relay API
Connecting to the Relay API
Connect your application to the endpoint of your project to make API requests. The Relay API provides several possibilities to fetch, modify or traverse your data.
Depending on your types and relations, certain automatically generated queries are available to fetch your data.
Traversing the data graph
Using GraphQL, you can select the individual fields that the response of a query or mutation should contain. The GraphQL schema of your project is built according to your types and relations and allows you to traverse the data graph in your query.
Depending on your types and relations certain generated mutations are available that allow you to modify your data.
If something goes wrong when sending a query or mutation, errors are returned in the response enabling you to further investigate the issue.