Q: how to find out what is documents and data

Hello johnfrombrooks,

Thanks for using Apple Support Communities.

If you'd like to learn more about what content lives in those storage categories on your iOS device, then please take a look at the information below.

Use iTunes to check the storage on your iOS device

1. Open iTunes and select your device. You'll see a bar that shows how much storage your iOS content uses, divided by content type. 
2. Hover your mouse over a content type, like Other or Apps, to find more information:
   

Here is a list of the types of content on your iOS device, and what each type includes:

• Audio: Songs, audio podcasts, audiobooks, voice memos, and ringtones
• Video: Movies, music videos, and TV shows
• Photos: Camera Roll content, Photo Stream, and Photo Library
• Apps: Installed apps
• Books: iBooks books and PDF files
• Documents & Data: Safari Offline Reading List, files created within apps, and app content like contacts, calendars, messages, and emails (and their attachments)
• Other: Settings, Siri voices, system data

See how much storage you've used on your iPhone, iPad, and iPod touch - Apple Support

Have a good one.