yes that is exactly what it is and vb and other forum software do use this feature, which I think is brillient and could really be effective in IPB. It's a way to allow users to join groups themselves as set by the forum admin. So if one wants to join a group called 'Premium Members' which would allow them access to certain forums after reaching 500 posts not allowable to Standard Members they could join this group and be approved by a Moderator or be auto-approved based on the admin's setting. This is a very nice way to upgrade members without having to manually switch them to another group as this would do it upon approval automaticly.
Definately a needed feature! +1 :thumbsup: