The purpose of social groups is to allow members more freedom and control over regular discussion with friends or people who share similar interests. However, while members are free to create groups and manage them as they wish, there are some limitations as to how they can be used, depending on the type.
Groups can be created by anyone who can create classifieds, that is members with 15 posts who have been a member more than one month. If you have just made your 15th post the permission wont activate for a couple of hours.
Groups are either "open" where anyone can join by clicking on the "Join group" button, or "closed" where clicking on "Join group" will send a special PM to the group owner to get approval. All posts from both types of groups are currently public.
Members who have joined can be promoted to "Group Lead" or banned from the group on the page listing the group members. Group Leads have the same permission in the group as the founder.