Half of my iPad Capacity is taken up by "Other"

Does anyone know what is included in "Other"? It's not audio, video, books, photos, apps, documents and data since I see how much storage all of those are taking up. I'm trying to free up space on my iPad so I can store more music and video and I can't figure out how to decrease the "other" category which is half of my storage.

Can anyone help me?

gdbnyc