What are the differences between group types?

Type	Description
	A public group is visible to everyone, and anyone can join or leave the group at any time.
	Protected groups are hidden from everyone except members of it. Restrictions apply to the group, message boards on the group, as well as boxes, trackers and events restricted to the group. Any member of a protected group can invite non-members into the group.
	A private group is almost identical to the protected group, except only group admins are able to invite new members to the group.