DVDBackup is intended to let you exercise your "fair use" rights under copyright law to either "time-shift" or "space-shift" DVD content which you may have purchased legitimately. An example of time-shifting would be to temporarily store the data from a DVD you rented so as to watch it at a later time after you have returned the disc (and avoided late fees!).
An example of space-shifting would be to copy one or more DVD discs to your laptop hard drive so as to watch them while on a long airplane flight. A final usage of DVDBackup would be to allow you to modify or excerpt sections of DVD video and audio to create your own movies.