Twitter announced today that it’s going to begin testing a new feature called Communities — a feature, that, as the name suggests, will allow people with shared interests to create groups about those interests.

In a post to its blog today, Twitter explains that only members will be allowed to post and reply to existing posts in Communities, which is how Facebook does it too. However, one major difference between say Facebook Groups and Twitter Communities are that Twitter Communities will still be public and visible to everyone. That means everyone on Twitter will be able to read or even Quote Tweet posts from a Community even if they aren’t a member of it.

Community posts can also be reported by everyone regardless of membership status. So, Communities aren’t private in any real sense, but more restricted for the purposes of keeping conversations focused on a specific topic. Twitter says that Community rules will be set by their moderators, who can also name other members as moderators. Communities, it comes as little surprise, have to follow Twitter’s rules, while moderators have a set of guidelines that they’re expected to follow in order to continue managing their Communities.

During the early stages of testing, Twitter says that Community creation will be restricted to just a handful of preset topics: dogs, weather, sneakers, skincare, and astrology. Twitter users will need to be invited by either moderators or existing members before they can join a certain Community, but Twitter says that it will open up more ways to join and recruit in the future.

For now, Twitter Communities are testing on iOS and web, with Android testing coming up soon according to Twitter.