A collaboration is anything where two or more youtubers are involved in making the video. (well, that's a loose definition, anyways). Most of the one's I have seen on here are indeed for gaming, but I've seen seen some on youtube with sketches and vloggers and stuff. It all depends on what kind of videos you want to collaborate on. And how.
If you are putting clips together you can do Q and A type stuff, a funny 'we interrupt this video to inform you THAT I HAVE TAKEN OVER *evil laughter* type thing, or anything really I guess. I've even seen one where vloggers accidentally 'switch' bodies. You can even do competitions/challenges with other youtubers, both posting your videos on your own channel. You can be really creative, but it will probably help you at this stage to know what kind of thing you are looking for.
I'm subbed to a lot of vloggers, and I've seen heaps of them do some great collabs. It would be really cool to be in one.
