This enables you to launch a website URL before exiting the patch process.
You can specify any URL here such as a domain (https://mysite.com) or (mailto:support@mysite.com) or even a MIME type you know is registered on their system to be launched.
It’s really good for launching a changelog webpage after a patch, or maybe an account page where the user logs in. There are many scenarios you could use the Launch URL feature for.