I was wondering where all the application data is stored on the Iphone ? I know there is an Application folder but that does clearly not hold all of the information.

Info: I'm trying to edit an application I've installed to see if I can improve it, I then plan on either using it solely on my Iphone or sending it to the original developer as an improved version of their software and allowing them to decide whether to release it.

I have no bad intentions in doing this and so I hope someone can/will help me out :-D