Help in understanding Video_TS and Video_RM files

I ave been given a DVD that was made for a group using Sony commercial gear. It contains a Video_RM folder that includes a *.BUP and a *.IFO.

It also contains a Video_TS folder that has Video_TS.BUP, Video_TS.IFO and a Video_TS.VOB files. There are also VTS 010.BUP, VTS 010.IFO and VTS 011.VOB, VTS 012.VOB and VTS 013.VOB.

Now I have extracted files from the Video_TS folder and have been able to use them in FCE.

But my question is what are these files?
Two of the VOB files are large and I assume they contain my video and audio.

Are they redundant?
Am I missing something by only extracting one of the folders?

What can someone tell me about these guys.

I did not see a reference to it in the FCE manual nor have I come across it yet in Tom's book on FCE.

Thanks

Dunc