When admins create communities, they are required to set community privacy settings. There are two options to choose between -- open and closed.
Open: When they make the community open, it means that it will be open to the public. That way, everyone who wants to join it will be able to do so automatically without waiting for the admins’ approval. Open channels can have community content publicly viewable without and indexed by Google or any other search engine.
Closed: When the community is closed, all prospective members will be required to send a request to join the community. They must be approved by admins to become members of the community.
Changing privacy settings
1. Click on Admin Panel.
2. Click on settings on the admin panel menu. Scroll down to the community privacy section to update your privacy settings
3. Click the Save settings button to save the changes.