The Schema Reference part of Banana Cake Pop allows you to learn about the types in your GraphQL API.
To access the reference click the dropdown where it says "Operations" and select "Schema Reference".
This will change the workspace area from "Operations" and "Response" to "Schema Reference" and "Types".
You will by default see the root "Query" type which has all the queries on your API. On the right hand side of the screen you can start to search for specific types to interrogate there specific fields.