You can visit other people and play with them or they can visit you. You can troll if you want but it's not nice to do it to strangers and they can kick you out. It would only be fun for 2 whole seconds.
It’s semi-open world, as the game has loading screens and invisible walls. It’s completely free roam though.
“There are no atheists in foxholes, eh?”-Keith Jennings from the Omen.