Merge pull request #13509 from github/ske-clarify-runs-on

clarify `runs-on` array

Author: ramyaparimi

content/actions/learn-github-actions/workflow-syntax-for-github-actions.md

@@ -475,7 +475,7 @@ In this example, `job3` uses the `always()` conditional expression so that it al
 
 ## `jobs.<job_id>.runs-on`
 
-**Required**. The type of machine to run the job on. {% ifversion fpt or ghec %}The machine can be either a {% data variables.product.prodname_dotcom %}-hosted runner or a self-hosted runner.{% endif %} You can provide `runs-on` as a single string or as an array of strings.
+**Required**. The type of machine to run the job on. {% ifversion fpt or ghec %}The machine can be either a {% data variables.product.prodname_dotcom %}-hosted runner or a self-hosted runner.{% endif %} You can provide `runs-on` as a single string or as an array of strings. If you specify an array of strings, your workflow will run on a self-hosted runner whose labels match all of the specified `runs-on` values, if available. If you would like to run your workflow on multiple machines, use [`jobs.<job_id>.strategy`](/actions/learn-github-actions/workflow-syntax-for-github-actions#jobsjob_idstrategy).
 
 {% ifversion fpt or ghec or ghes %}
 {% data reusables.actions.enterprise-github-hosted-runners %}