it's a "Minecraft"-esque game where people create games within the game and then people can join in and play them.
It's honestly something I've played twice with my daughter. She will endlessly watch a specific group of people on Youtube get together and play the game online (which is honestly more entertaining at times than I care to admit), so I decided to install the game on my computer, create an account and join her in the game so she would actually play the game more often instead of just watch others play.
It's really basic "Lego/Minecraft" looking game, and at times filled with hacking little kids who want to ruin everyone else's fun for their own, but even in it's simplicity, it's pretty fun and addictive as you can jump from game to game within the game and find somewhat new experieces all within the same game endlessly.
One that I played was one where you can be either the prisoner or the police. As a prisoner, you need to pickpocket an officer for a gun and/or security card, and then escape the prison. Once you escape, you can steal cars/vehicles, rob stores and a museum, and then cash it in for loot to buy stuff, like better cars, guns, clothes, apartments.
Another was a "horror house" game where you enter a game of everyone kill the monster. One player is chosen at random to be the monster, and you must kill everyone, or everyone must kill you.
both were surprisingly addictive, fun, yet simple.
and there were probably another 1000 games in there I wasn't even about to take the time to dive into.