Users can be members of more than one group. Consider a site with two groups (see diagram below). Group 1 has a group administrator, Avi, and a second group member, Ben. Avi also belongs to Group 2, this time as a regular member.

Groups can be configured so that users can join ("subscribe"), either automatically or with administrator approval.

An anonymous user can join a group, but she must first create a user account on the site.