iCloud is Apple’s innovative new service that stores your content and wirelessly pushes it to your devices.

iCloud stores your music, photos, apps, calendars, documents, and more. And wirelessly pushes them to all your devices — automatically. It’s the easiest way to manage your content. Because now you don’t have to.

iCloud automatically backs it up each day over Wi-Fi. But rather than backing up your information from scratch, iCloud uploads only what you’ve changed. It’s quick and efficient, and it makes Backup like everything else in iCloud: convenient and completely effortless.
iCLoud backs up your Purchased music, apps and books, Photos and video in the Camera Roll, Device settings, App data, Home screen and app organisation, Text and MMS messages, Ringtones.

Visit the Apple website for more information.