DonB2
no need to be sorry and your questions aren't wierd at all. They are very valid. The structure of commercial DVDs are very interesting (at least IMHO they are).

If you look at the DVD structure you will see 2 directories. There is a Video_TS where all the video files are and an Audio_TS directory with the DVD audio. Inside the Video_TS directory you will find .IFO .BUP and .VOB files The .ifo files are the information files that OTAHD indicated above. The .ifo files provide direction or navigation instruction to the player so it knows where the actual movie and audio files are and when to play them including linking to the DVD menus and chapters. Kind of like bookmarks. Like OTAH said, your player reads the .ifo and gathers the components needed to play. The Sony problem is called "ARccOS" which places instructions ( bad sectors) to video objects that do not really exist. Your DVD STB no matter how old will just skip over them where most ripping programs like Shrink, etc, will try to find them and then error out.

Then you have .BUP files. .BUPs are just backup files of the .ifo information. BTW, both .ifo & .bup files are not encrypted. Talk about wierd, if you delete or don't include any of the .bup files the movie won't play. I'm still not sure why. Anyone that knows, please feel free to chime in.

Next and most important are the .VOB files or video objects. These are the actual movie files that can or do contain many different streams multiplexed together (video, audio, sub-titles, etc.). You can copy a .VOB and just rename it with an .MPEG or .MPG extension and it will play on your PC.

If you're really interested there are some wonderful explanations and papers at doom9.net. definately worth checking out.