Usually it means a host backs up a mirror image of the contents of your boxes to tape every week. So if something fails, hard drive etc you can revert to the last back up seemlessly.
Essentially its a mirror image of your server backed up like a snapshot in time if something goes horribly wrong.
Not sure how webair works but we have daily backups with another provider... databases, sites, everything essentially. Plan for the best but prepare for the worst.....
