You can pretty much join any world, just select which looks cool from a list and you'll get teleported into a public instance of that world, where there's usually 5-20 people. It can take a minute to find a good crowd (i.e. no kids), but the overall culture is very welcoming and chill.
There are campfires, aquariums, movies, or you can just drift into the cosmos listening to a 4 foot tall anime cat perform live music for everyone.
