Tell me about Password Protection...

I'm going through the available policy settings for edge, getting a policy ready ahead of the upcoming release, and saw these settings related to password protection.  

https://docs.microsoft.com/en-us/deployedge/microsoft-edge-policies#passwordprotectionwarningtrigger 

https://docs.microsoft.com/en-us/deployedge/microsoft-edge-policies#passwordprotectionloginurls 

https://docs.microsoft.com/en-us/deployedge/microsoft-edge-policies#passwordprotectionchangepasswordurl 

I understand that this will trigger warnings if the user enters their "Protected Password" on a site other than those listed in the policy, but I don't see anything explaining what makes something a "protected password".  Is it their AD/AAD password?  Or can they specify passwords to be protected?  Or...?

Other than the description of the policy setting itself, I can't find any information on this password protection feature of Edge.  Is there any documentation out there explaining more about it, or can anyone in the know share info on it?