When connecting your iPad/iPhone to your computer you’ll see on the bottom of the Summary page, in iTunes, just what’s taking up space: Audio, Apps, Photos Other. The dreaded "Other" the mysterious "Other."
This storage section has puzzled many a tech writer and developer (even Apple Support). “Other”, which may take up considerable space on your device, consists of things like cached iTunes content (streamed movies, for example), Mail data, and Safari website data.
You can try to delete some of this, but unfortunately it’s not always possible. In fact, there doesn't seem to be a way to delete cached iTunes content.
The only way to effectively delete "Other" data is to back up and restore your device with iTunes. Backing up is a good habit to get in to not matter what. This process will retain all of your apps in the cloud while deleting any extra junk files that may exist. You'll lose some data like game save files, but it's the only way to reclaim storage claimed by “Other”.