iTunes has 8 standard data categories listed in the Data Bar of iTunes. They are called Apps, Music, Movies, TV Shows, Podcasts, Books, Photos, and Info. Basically, anything stored on your iDevice that cannot fit into one of those 8 categories is categorized as "Other." This includes:
1.Browser cache
2.Mail cache
3.Mail messages
4.Mail attachments
5.Safari's Reading List
6.iTunes Backups
7.Crud resulting from jailbreaking your iDevice
8.Game data
9.Saved data files
10.Call history
11.Notes
12.Media
13.Voice memos
There are two main ways to remove this data from your iOS device.
The best method is to wipe your device. Back up up your iPhone on iTunes first, then go to Settings > General > Reset and choose Erase All Content. Then connect your iOS device to iTunes and restore from backup. These steps erase all the cookies, temporary files and so on.
If you don’t want to wipe your phone, but still need to regain some of your storage space, you can
Delete & reinstall Apps with bloated local data (such as Facebook, Twitter, Instagram and Flipboard);
Open Settings, then go to “Safari” and tap on “Clear Cookies, Data, History”
Hope this is helpful.