Course backup files are backups of individual courses. The backup file in moodledata/1/backupdata is the backup file for course #1 (the front page of your site is also a course!).
You COULD restore an entire site from these files, but you would have to do so by restoring each course manually from its backup file, including course #1. If you have only a few courses, it might be practical to do it this way.
You COULD also migrate a site to another server using the individual backup files. But again, you would do so by restoring each course manually from its backup file on the new site.
If you have more than a few courses, it's better to make a backup of your database (as an SQL file) and your moodledata directory. Search the forums for advice on exactly how to do this (it is a frequently asked question).
Backup and restore
Confused about Buckup and Restore.
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