Visibility: decide whether your forum is public, private or hidden.
Public – Anyone can see these forums
Private – Only logged in registered users can see these forums
Hidden: Only Moderators/Admins can see these forums
I had created 3 forums, one of each visibility-option. But I (as logged-in admin) could only see the public forum. In the frontend I only see the public-forum in my top-menu. I also tried to add menu-entries for the other forum in my WP-custom-menü, but both forums didnt appear in the menu-creation (design / menu).