The All Users
Role is not technically a role that can be managed from the Roles
page, but it does control who can access features on a web site running on DotNetNuke.
If you apply VIEW permissions for the All Users role in a Permissions_Grid
you are saying that anyone visiting the website, logged in or not, can view whatever that permissions grid applies to.
Another virtual role is Unauthenticated Users
role, which is applied to anyone, who currently is not logged in.