iTunes - What's in the 'Other' Category?

After syncing my iPod from iTunes, I noticed that I now have *1.49 GB in the 'Other' category,* 5.41GB in 'Audio' category, 367.1 MB in 'Video' category and 152.5 MB 'Free'. Total capacity 7.41GB (8G nano).

I have no shows, pictures, podcasts,etc. All I have are songs and videos.

So, what's in the 'Other' category/folder, and why is it so large?
I do not remember ever explicitly putting anything in 'Other'.
How can I get delete stuff from it - or should I delete stuff from it (the 'Other' category/folder')?