You can validate a change set without deploying changes. By validating you can view the success or failure messages you would receive with an actual deploy.
A change set is deployed in a single transaction. If the deployment is unable to complete for any reason, the entire transaction is rolled back. After a deployment completes successfully, all changes are committed to your org and the deployment can’t be rolled back.
Knowledge Article: Validate a Change Set
https://sforce.co/2J0UtK8
Knowledge Article: Deploy a Change Set
https://sforce.co/336Rvuf
Watch the next video in the Change Set series here:
https://bit.ly/396JVnh