what is the "other" section on my ipod memory

It is items that do not fit into the categories that are specifically listed. If it is large. like greater than about 3/4 GB, it contains corrupted file. To reduce the "other" category you need to restore the iPod.

Everything that is not music, video, photos, apps, or unallocated. It includes in-app data, iOS, notes, contacts, calendar info...