VOB stands for DVD Video Object. It is basically one of the core files found on DVD-Video discs and contains the actual movie data.
Basically VOB file is just a basic MPEG-2 system stream -- meaning that it is a file that contains multiplexed MPEG-2 video stream, audio streams (normally AC3 and DTS formats) and subtitle streams.
In order to view stand-alone VOB files, you need to have a DVD player software that supports VOB playback. A good, open source tool for this is Media Player Classic. If you wish to burn the VOB files to a standard DVDR disc, you need to have all the other standard DVD files as well, including IFO and BUP files. If you have all of the required files, you can follow this guide in order to do so with freeware tools.
Related software tools
Corel WinDVD (Commercial demo)
WinDVD is a powerful software DVD decoder/player with very good picture and audio quality.