Those are movie files. VOB (Video OBject files) contain video, audio, and subtitles. IFO files contain indexing and navigation information, and BUP files are backups of IFO files. Check out the
DVD Demystified FAQ for more information.
With some players, you can select the VIDEO_TS.IFO file and achieve proper dvd playback. However it is more common to point your dvd player to the directory containing the DVD files. If you're using mplayer you can use the command:
Code:
mplayer dvd://1 -dvd-device /dev/hdc
replacing /dev/hdc with your dvd device or mount point.