Use public, private, or unlisted Chatter groups to collaborate with specific people in your company.
Chatter Groups Chatter groups let you collaborate with specific people. For example, if you're working on a team project, you can create a group for your team to share project-related files and information. Group feeds in Lightning Experience are live feeds that update in real time. They don’t require a page refresh to update.
Unlisted Groups Overview Unlisted groups offer more privacy for compared to private groups. Only group members and users with the “Manage Unlisted Groups” permission can access unlisted groups in list views, feeds, and search results.
Broadcast Groups Broadcast groups are a special type of public, private or unlisted group where only group owners and managers can create new posts. Group members can comment on the posts created by the group owner or manager.