can you actually go anywhere in this pic, or is the game somewhat linear in that regard?
It's not exactly linear, but what you are looking at here is a character standing in the hub "town," and overlooking what is essentially an incredibly detailed skybox.
But when you go out into the world, it's just an open environment where you can go wherever, more or less, and encounter other players just doing there thing, like an MMO. So I wandered around and found an area with incredibly high level characters that I couldn't do anything in but die, for example. There are story missions that take you through a linear progression inside of those environments, that eventually put you in the sort of equivalent of an MMO instance.