I'm a little confused about the process of backing up files from my iPad 2 to iTunes on my laptop. Recently when I connected the iPad to the laptop and told iTunes to sync it, it seemed to me that the result was that the contents of the iPad was made the same as what had been on iTunes. So some app data that had been on the iPad appeared to vanish. I definitely don't want to do this. When I sync, I don't want the contents of the iPad touched in any way. Rather, I want to make a copy on the laptop of everything on the iPad, including app data and working files. Is there something I need to know about how to do this?