Backup is based on your account and has nothing to do with the information on the phone. When you do a restore it re-installs all the apps and data. That's if the data is backed up.
Keep in mind that any personal data backup should be up to you and I wouldn't rely on the phone backup for it. Not all data gets backed up.
That's not including contacts and emails which is backed up easily. I'm talking photos, videos etc. Game data will be wiped unless there's a system in place to back it up.