Facebook sync and backup are additional ways to get your photos into your Forever™ Account. All of your photos from Facebook will also be given a “Facebook” tag to help find and identify them as well.
Facebook backup is an action you perform once to bring in all of your publicly available Facebook photos to your Forever account. This will bring in photos that you posted however, it won’t bring in photos from groups, pages, or messages.
Facebook sync is forward looking and can be toggled on or off. While it is turned on, Facebook sync will bring in any photos that you post. You can disable it at any time.