I've never really used itunes before and have never used an ipod. Can anyone explain how syncing your device works? Can I sync it on multiple computers, or will it wipe out the information on my device if I sync it to a second computer?

My question has to do mostly with mp3s, photos and maybe even calendar information. If I load it all onto my iPad on one computer, and then sync it at work, will it backup the iPad and sync the contents across multiple computers? Or if my main computer has a hardware failure and I have to replace the computer or hard drive, will the new computer pull the information off of the ipad, or does the sync only go one direction?

Can current devices work as a portable hard drive? If I have photos on it, can I transfer the photos to my father's computer?