What does Other mean while syncing on iTunes?

I my iPhone has 1.29 gigs of other and i'm not to sure what that is.

Well by my understanding it is the software, messages, etc. Like when you upgrade an iPhone 4/4s to iOS 6 the "other" increases a lot. So i'm pretty sure "other" is just software like iOS, the stock apps, messages, notes, etc.that's why i haven't upgraded my iPhone 4 to iOS 6 because i need as much memory as i can get:/