Each time you connect your iPad or iPhone with iTunes, iTunes updates a backup on your computer of all your contacts, text messages, calendar, notes, call history and app data.
If you've accidentally deleted some of the information from your device and are hoping to recover it, this backup can be a great help. If you're in this situation, don't sync your device. Syncing may delete the information from the backup too.
So where are iPad/iPhone backups stored? It depends on which operating system your computer is using. Although the default backup location is the same between iOS and iDevice, whether you have an iPhone or iPad and whether you have an iPhone with iOS 6 or iOS 5 installed.
\Documents and Settings\USERNAME\Application Data\Apple Computer\MobileSync\Backup
Mac OS X
To see what's in your backup, why not download the free iPhone Backup Extractor?