Setting the policy lets videos play automatically (without user consent) with audio content in Google Chrome. If AutoplayAllowed policy is set to True, then this policy has no effect. If AutoplayAllowed is set to False, then any URL patterns set in this policy can still play. If this policy changes while Google Chrome is running, it only applies to newly opened tabs.
For detailed information on valid url patterns, please see https://cloud.google.com/docs/chrome-enterprise/policies/url-patterns.