iCloud automatically backs up your iPhone data, but what exactly is uploaded to Apple's servers for safekeeping?
iCloud backs up and gives you unlimited space for:
Purchased music, apps, books, movies and television shows. Previously purchased items may not be restored if the item is removed from the store.
iCloud backs up and allows 5 GB free storage for:
Home screen icon layout and folders
iOS Settings (including Calendar accounts, Contacts, Favorites, Mail and Wallpaper)
Messages including iMessage, MMS and SMS (text messages)