As the name implies, BackupHDDVD is a program that allows users to copy HD DVD movies. The program is significant because it thwarted the impenetrable HD DVD DRM AACS (Advanced Access Content System) by simply going around it. Rather than breaking AACS’ copy protection, BackupHDDVD attacks HD DVDs from the content protection side.
If you’re still scratching your head over all the hoopla caused by the release of BackupHDDVD then check out this interview with muslix64, the developer of the program. I won’t guarantee that it’ll answer all, or any, of your questions, but it’s a decent read for anyone interested in HD DVD.