While purchase history of apps, books, movies, music, and TV shows will be saved, the content itself will not be automatically re-downloaded after restoring from an iCloud backup. Additionally, any content that was not purchased from iTunes, photos that weren't stored in the local Camera Roll, your call history, home screen setup, and other data will not be backed up using this method.
For a complete backup of your iOS device, you'll want to use iTunes.
Almost all of your data and settings will be backed up using iTunes. The content that won't be included are photos stored in the cloud (My Photo Stream and iCloud Photo Library), your Touch ID information, and Apple Pay information and settings. Activity, Health, and Keychain data also won't be saved unless you use an encrypted backup, which we'll go over.
Apps, iTunes purchases, and PDFs also won't be included in the backup, but these can be seamlessly restored by syncing content on iTunes, which many of you might already have set up.
While iTunes is great for syncing content that uses up a lot of space or doesn't need immediate updating, information that's edited or changed more often, like Mail, Contacts, Calendars, Reminders, Safari, Keychain, and Notes, should be synced via iCloud by going to Settings -> iCloud and toggling them on. That way, all of your important data syncs between your iOS devices and Mac computers without taking up a lot of iCloud storage.
How to Create an iTunes Backup
With your iOS device connected to your computer, launch iTunes, then select your device from the options under the play controls. If this is your first time connecting your device to iTunes, you'll need to select "Yes" on your iOS device when prompted, as well as input your passcode on your iPad, iPhone, or iPod touch.
Under the section labeled "Backups," click the "Back Up Now" button. This will only take a few moments and will create a full backup on the spot.
If you wish to automatically back up your device to the computer—instead of iCloud—any time it's connected, check "This computer" located beneath "Automatically Back Up."
Encrypting a Backup
If other people use your iTunes and computer, or you wish to also include information like account passwords, Health, and HomeKit data, then create an encrypted backup. If you don't encrypt your backup, you'll be required to enter all of your passwords for apps, many of which you may have already forgotten. (Tip: use an app like LastPass to store your passwords on iOS.)
For this option, just check "Encrypt iPhone backup," create a password, then click the "Set Password" button. This method will take a little longer to complete, but it's worth it if you need it.
Restoring an iTunes Backup
When it's time to restore your device using iTunes, the process is just as simple. Start by connecting the device to your computer and launching iTunes. On the same screen where you created the backup, just select "Restore Backup."
iTunes will automatically choose the latest backup created, but if you have a different one you wish to select, just expand the drop-down menu to view other backup files stored on your computer.
After clicking "Restore," wait for the process to finish. Your device will restart then sync with your computer, so make sure it remains connected throughout.
Using Backups on Different Devices
Whether you're attempting to use an iPad backup for an iPhone or an iPhone backup for an iPad, it's worth noting that some of the content will not successfully transfer over. This content includes photos, messages and their attachments, voice memos, and apps that are incompatible with the device (for example, some apps are only available on iPhones, not iPads).
Both backup methods have their advantages. Although iTunes lets you save more content, it doesn't provide the on-the-go convenience that iCloud backups do. Additionally, using iCloud grants you the ability to restore deleted content on your iOS device. But since you're not restricted to only using one method, use them both to ensure you're always covered.