This is a feature for Admins only.
Groups can behave differently depending on their Group Type. Here you can create Group types like 'Invite Only', 'Secret', 'Open' that can be applied to future groups. You have full control over what attributes these Groups have.
To create and manage Group Types, go to Settings > Groups. You’ll now see a list of Group Types that are currently set up on your system.
To create a Group Type, click on Create group type – you’ll now see this screen:
Here you can choose whether a group is visible to others, if it is invite only and who has permission to create it. You'll also have a chance to name it. For example, if you create a group type that only admins can see, you might name it 'Secret'.
When users create a new group or edit an old one, they will be able to choose their Group Type from those that you’ve created.