This feature allows you to create quickly a backup copy or to restore your WordPress website from the last successful backup copy created by WP MyBackup. It also allows you to upload an external backup archive (tar, tar.gz, tar.bz, zip) created by itself of by some other backup application then allows you to restore it.
Example: your backup contains a folder like /home/userABC/mywebsite/wp-admin/ and some files within it. When this folder is restored it will be restored as-is in your WordPress root folder despite the fact that you might expect that it will discard the /home/userABC/mywebsite prefix. So make sure your archive path is relative to the WordPress root path.