Twitter Communities is Twitter’s Facebook Group-like feature where admins can administer groups of users centred around a specific topic.
Anyone on Twitter can see the conversation, but only members of the group can participate. Tweets are not distributed to your followers and don’t show up in your profile.
Twitter Communities launched in September 2021 on iOS and the web, and is now available today on Android also.
The feature is integrated into the Twitter client. Read more about it at Twitter here.