Public groups can be used by anyone in the company, for example, to choose as an audience for posting Shoutouts.
To choose a group as the audience for a Shoutout, the group must be made public 🙂️
But rest assured, when you post the Shoutout for that public group, only they will be able to see the Shoutout on their homepages!
Private Groups are mainly used by Admins (or the people who are chosen to have visibility over those Private Groups), to make it easier to access a certain group of people without the need to create a set of conditions and rules over and over again, such as selecting participants in a performance cycle, permissions, settings (practical examples, to create groups of Remote vs In-office vs Hybrid; Identify contractors; etc).
You can use the private group in advanced filters - both in the reports and in the directory and select them easily in comp, surveys, performance, task lists, flows, etc.
If you'd like to know more about this, please check our Help Center page: Create a group.