As far as we know it is an open world RPG with maybe a co-op. One thing that has been passed around SWTOR forums and podcasts is the idea that if SWTOR had launched calling itself a single player game but with multiplayer elements in it then it would have been able to weather the broken state it was given to us as the public at large may have been gentler of major MMO features missing i.e. broken trade network, lackluster crafting system that almost prohibited selling your wares, and major missing elements of guild management functionality. The reason I bring this up is that I HOPE that this game launch includes enough multiplayer elements that I can get my MMO fix from it even if sold as a single player title.