What's the difference between backups and syncs?

Backup
_________________________________________________________
A Backup performs (in the simplest terms) a file backup of your device. It should contain all your settings, contacts, MMSs and just about everything else... EXCEPT for jailbreak info and programs from Cydia. However, it will keep the settings for those programs (such as high scores, settings, etc if the program was built correctly in the first place). One thing it does not restore is media files such as video and audio. (It will restore pictures)

To Backup the device (if you phone does not do it automatically), connect to iTunes and right-click (Option+Click) on the iPhone, and select "Backup".

To restore the device's info (makes no changes to current jailbreaks, unlocks) to an iPhone, it should give you an option after a OS restore which asks you if you want to setup the phone as a new iPhone, or if you wish to restore from a backup. If you have a different phone you want to restore the backup to that has already been setup before, you won't get this option when you connect to iTunes. Instead, Connect the iPhone to iTunes and right-click (Option+Click) the iPhone name and get the option to "restore from backup..." Likely it will not give you the update times of the backups, but the top option will be the most recent. It helps if you BACKUP your old phone before doing this.




Sync
_________________________________________________________

The 'Sync' Option will do just that... Synchronize chosen info between the device and your computer (or otherwise set settings). Loosely, a sync will copy your contacts from your computer (usually from Outlook or your other favorite contact program) to the device. It will not restore photos, text messages, settings, or any other data than the info you select for that phone within iTunes. To change those settings, select the iPhone in the devices list in iTunes, and select the appropriate tabs.

To sync (if not setup automatically), press the sync button in the lower right of the iTunes window, or right-click (Option-click) the iPhone in 'devices' and select sync, or press the sync icon next to the iPhone in 'devices'.