[docs] Update composition errors docs

docs/source/errors.mdx

@@ -4,13 +4,19 @@ description: Learn the error codes you can receive if composition fails.
 toc: false
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-When Apollo Gateway attempts to compose the schemas provided by your [subgraphs](./building-supergraphs/subgraphs-overview/) into a supergraph schema, it confirms that:
+When GraphOS attempts to compose the schemas provided by your [subgraphs](./building-supergraphs/subgraphs-overview/) into a supergraph schema, it confirms that:
 
-- The subgraphs are valid
+- The subgraphs have valid GraphQL and Federation syntax
 - The resulting supergraph schema is valid
-- The gateway has all of the information it needs to execute operations against the resulting schema
+- The graph router or gateway has all of the information it needs to execute operations against the resulting schema
 
-If Apollo Gateway encounters an error, composition fails. This document lists subgraph validation and composition error codes, along with their root causes.
+If composition fails, a new supergraph schema cannot be generated. This document lists subgraph validation and composition error codes, along with their root causes.
+
+<Note>
+
+Composition may flag potential improvements or _hints_ on schemas which are technically valid. These hints aren't  errors, and are instead logged as part of the composition build step.
+To learn more, see the [composition hints doc](/federation/hints/).
+</Note>
 
 ### Errors
 
@@ -1633,4 +1639,4 @@ Subgraph definitions for a union are now merged by composition.
 </td>
 </tr>
 </tbody>
-</table>
+</table>