Menu VOB's

On most occasions a DVD will play the VIDEO_TS.VOB first when you insert it and then any relevant Titlesets (see pic below) before reaching the Main Menu (VTS_01_0.VOB).

The other Menu VOB's (VTS_02-06_0.VOB)will be played when you select them from Main Menu

Main IFO/BUP & Titlesets

The Main IFO/BUP is the heart of the DVD and contains the information the tell the DVD what to do when it first plays. A BUP file is an exact copy of the IFO file

The Titlesets a.k.a. Vobsets contain the video of the DVD. Normally the largest Titleset contains the Movie which are VTS_01_1-6.VOB in the picture