Site AdminsInherited Group
This group includes people who are not signed in.
They cannot create and edit their own conversations, events and comments.
They cannot update items created by others.
They cannot delete items created by others.
Membership groups control access and permissions within a forum.
People start with no permission to do anything, and are granted permission by being a member of a membership group.
The vast majority of people are either guests (not signed-in) or members (signed-in).
The default groups are site-wide, and all new forums have these groups. If a forum has it's own custom membership groups, then these may override the defaults and allow for private forums.