(User manual)

140 Appendix A Troubleshooting
Backing up iPhone or restoring from a backup is not the same as syncing content
and other items (such as music, podcasts, ringtones, photos, videos, and applications
that you download via iTunes) with your iTunes library. Backups include settings,
downloaded applications and data, and other information that resides on iPhone.
You can restore these items from a backup using iTunes, but you may also have to sync
your iTunes library content again.
Applications downloaded from the App Store are backed up the next time you sync
with iTunes. Afterwards, only application data is backed up when you sync with iTunes.
Creating Backups
Backups can be created in the following ways:
Once iPhone has been configured to sync with a particular computer, iTunes 
automatically makes a backup of iPhone on that computer when you sync. iTunes
won’t automatically back up an iPhone that is not configured to sync with that
computer. If you have configured iPhone to automatically sync with iTunes on a
specific computer, iTunes will back up iPhone every time you connect it to that
computer. Automatic syncing is turned on by default. iTunes only makes one backup
each time you connect, even if you sync multiple times before disconnecting.
If you choose to update the software on iPhone, iTunes will back up iPhone 
automatically, even if it is not configured to sync with iTunes on that computer.
If you choose to restore the software on iPhone, iTunes asks if you want to back up 
iPhone before restoring.
If you use a Bluetooth headset or car kit with iPhone and you restore settings, you
must pair the Bluetooth device with iPhone again to use it.
Restoring from a Backup
You can restore the settings, downloaded applications, and other information from a
backup, or use this feature to transfer these items to another iPhone.
Restore iPhone from a backup:
1 Connect iPhone to the computer you normally sync with.
2 In iTunes, select iPhone in the sidebar and click the Summary tab.
3 Click Restore to reinstall the iPhone software, restore its default settings, and delete
data stored on iPhone. In iTunes, you can also restore from a backup without deleting
data stored on iPhone.
Deleted data is no longer accessible via the iPhone user interface, but is not
permanently erased from your iPhone until it is overwritten by new data. For
information about permanently erasing all content and settings, see “Resetting
iPhone” on page 109.