This article is an overview of how to sync the following devices with your computer and where to get additional information.
When you connect your device to your computer, items automatically sync according to your preferences set in iTunes. You can, for example, enter email addresses of friends and family members on your computer, connect your device to sync, then unplug it and tap a friend’s email address on the touchscreen to email them.
You can sync
Contacts—names, phone numbers, addresses, email addresses, and so on
Calendars—appointments and events
Notes (sync with Mac OS X Mail* or Microsoft Outlook)
Music and audiobooks
Movies and TV shows
Ringtones (iPhone only)
Books (iPad only)
iTunes U content
Note: On iPad, you can also sync documents via File Sharing with apps on iPad that support it.
You only need to set which items are synced in iTunes on your computer once. After that, just connect your device to start a sync.
Contacts, calendars, notes, and bookmarks are synced from (or to) your computer, so if you add, change, or delete them on the device, they are changed on your computer, and vice versa. You can also sync contacts with your Yahoo! or Google Address Book.
Email-account settings, music, movies, TV shows, podcasts, and photos are synced one-way, from your computer to your device (though you can import photos taken with iPhone to your computer and you can transfer purchases from your device to iTunes). Using an iPad, you can send photos back to your computer (typically captured on iPad via the Camera Connection Kit).
If you like, you can set your device to sync with only a portion of what’s on your computer. For example, you might want to sync only a group of contacts from your address book, or you may want to sync only songs from certain playlists so you don’t fill your device with your music.
* Syncing is over USB only and on a Mac requires Mac OS X 10.5.8 or later.