You can select an area in the world , where to put ennemies and objects in the environment.Create plateform missions, escort mission, killing missions, shooter missions ( invaders style ); free parkour missions. And make custom trpohies If m correct.
Then whenever you play in the world, you can see on the radar new missions created by players and join them. I guess the world will be constently online.
Are you in the beta? Looks very promising from the vids I've seen.