|Using a Jive Community / Using External Groups|
An external contributor can join a secret or private group when invited into the group by a group member. External contributors can view and participate only in that group. They cannot see any other community content or activity, and they can only join a maximum of 20 groups.
You can securely invite someone from outside your community to participate in an externally accessible group. The standard community user can only see external contributors when they belong to the same group.