The Encrypt Backup feature in iTunes locks and encodes your data. An encrypted iTunes backup includes certain information that other backups don't:

• Your saved passwords
• Wi-Fi settings
• Website history
• Health data

iTunes doesn't encrypt your backups by default. To encrypt a backup in iTunes for the first time, you'll need to turn on the password-protected Encrypt Backup option. After you turn on Encrypt Backup, iTunes automatically makes encrypted backups for that device from then on.
 

There is no way to recover your information or turn off Encrypt Backup if you lose or forget the password.

You can also make a backup in iCloud, which automatically encrypts your information every time.