
Looking at the patch notes on the Grounded forums, you can only own up to three Shared Worlds at any given time, but you can have up to 50 shared with you, although we imagine you'd be hard-pressed to fill that quota. Obsidian even says that this feature works between each store's version of the game: Xbox, Microsoft, and Steam.

It allows you to essentially share a copy of your save game with your pals, which they can download to their own game, but as a standard copy. By using the Cloud for World Sharing, you and your friends will be able to share the same world, whether the original creator is there or not.
