What I've been using: Imagine you and your friends have a noticeboard and you can post stuff on it. People can choose to host their own noticeboard too. If you'd like, you can also follow posts made on other noticeboards so that when it's posted there, a copy of the post is made on your board too. If you run your own board, you can choose to block boards you think are offensive to the people using your board. That way the offensive posts from there don't appear on your board.