What are the differences between private and members-only groups?
Private and members-only groups are both user-controlled but differ on one point: who can use the groups. Private groups are just that, private; only the user who creates a private group will be aware of its existence and be able to use it. Members-only groups may be utilized by the owner of the group and anyone who is a member of the group. For instance, a department might task one individual to construct and maintain (people leaving, new hires, etc.) a members-only group of their entire department. This way, only one person need maintain the group and anyone in the department will be able to utilize that group.