Add explanation of the GraphOS key

Author: jcaudle

docs/source/command-reference.mdx

@@ -143,7 +143,7 @@ All fields are optional and have sensible default values.
 
 #### GraphOS configuration
 
-These fields are under the top-level `graphos` key.
+These fields are under the top-level `graphos` key and define credentials and other details related to GraphOS.
 
 | Option                    | Type     | Default | Description                                                                                                     |
 | :------------------------ | :------- | :------ | :-------------------------------------------------------------------------------------------------------------- |