Phones and tablets usually come with an operating system that's fairly limited in what it lets you do. Part of that is to make sure people don't screw their electronics up because they don't know what they're doing, but another part is to control what you can do with it. For example, the iPad doesn't let you install software on your own, you need to get it from the App Store. And the App Store (a) makes sure that software won't brick your tablet, and (b) gives Apple a 30% cut of what you pay for things in the App Store or on things you buy via apps.What does "root your tablet" mean?
"Rooting" is short for "give you root access", with "root" denoting a user in Unix/Linux systems (on which I believe iOS is based) who can do whatever the heck they want with the system. This would allow you to access the actual file system on the device (as opposed to the filtered version you normally can, where any data is locked off to a certain app), which is what you'd need to extract said data.
For example, on my computer I have a Documents folder in which I can organize my data pretty much as I please. I can have a DnD folder there, with maybe an Eberron subfolder. In this subfolder I can put pretty much anything I want – I can have PDFs of old sourcebooks, I can have my own notes about an adventure in Word or Open Office Document format, I can have maps in PNG or JPG format, or whatever else strikes my fancy. If I double-click on elaydenbrev.doc, my computer will open that document in OpenOffice Writer (because I have it set up to do that) and I will see the handout I wrote back in 2005. If I double-click on Sharn_Web_Enhancement.pdf, my computer will open Acrobat Reader and display the web enhancement for Sharn, City of Towers. And if I click on Ulfkort.ppt (originally a Powerpoint file), my computer will open it using OpenOffice Impress and I'll see the cards I once made for a player who played a Soulknife, which meant they had use of cards to keep track of whether they had Psionic Focus and/or Psychic Strike online or not. And for each of these files, there are many different apps I could use to read and/or edit them, and I'd still be able to access the files regardless of app (as long as that app can read that file format, of course – trying to open a PDF in Notepad wouldn't do much good)
On the iPad, things work differently. I'd have to first open the relevant app, and from there I would have access only to things belonging to that app. So elaydenbrev would be under Pages, Sharn_Web_Enhancement under Acrobat, and Ulfkort under whatever app the iPad uses for presentations. And switching to different apps in case I find I'm not happy with one would probably not be impossible, but likely require some effort.