This is Fallout 4's official launch trailer. It provides much more insight into what you'll actually be trying to accomplish in the game. Apparently The Institute, that mysterious advanced technology organization plays a major role, because they've created near human-like androids ("synths"), and a lot of humans aren't happy about it. Still, regardless of what I'm SUPPOSED to be doing, I can guarantee I'm gonna spend the majority of my time eating as many squirrel-on-a-sticks as I can and trying to bang a super mutant. I have priorities.
Keep going for the video, pretty sweet tree-house around the 0:27 mark. I'll definitely be spending some time there.