November 12, 2011, 8:30 AM — Thanks to the combination of iTunes 10.5, iOS 5, and iCloud, you can sync data wirelessly with your iOS device. In fact, there are two ways to do so: iCloud syncing, which sends specific information to and from Apple's iCloud servers over an Internet connection, and Wi-Fi Sync, which syncs your device with iTunes on your Mac via your local wireless network.
But there are notable differences between what gets synced using each method--some things are exclusively iCloud or Wi-Fi Sync, while other things can be synced via either method. And it's important to note that Wi-Fi sync and iCloud sync aren't mutually exclusive. You can, and mostly likely will, use both methods depending on the situation and your settings. Which is why it's easy to get confused about the differences and similarities between the two.
Here's a quick summary of the types of data handled by each, as well as when each type of data is copied or synced.
Wi-Fi syncing is identical to tethered (USB) sync--it syncs only data that resides on your Mac. You enable Wi-Fi sync, counterintuitively, by connecting your iOS device to your Mac via Apple's USB-to-dock-connector cable, and then, in iTunes's Summary screen for your device, checking the box to Sync With This Device Over Wi-Fi.
Wi-Fi syncing can sync the following types of data between your iOS device and iTunes. Note that, as with USB syncing, Wi-Fi syncing handles only those categories of data you've chosen in iTunes to sync to each device.