An MDS file is a media descriptor file that is normally generated with MDF files during the creation of a CD or DVD disc image.
The MDS itself is just a binary file with a "media descriptor" which contains all the metadata about the original file, including layer breaks.
The file is needed to re-create the DVD or CD and uses the .MDS extension.
MDF and MDS are proprietary file types of Alcohol 120% but can be burnt or mounted using Nero, IMGBurn or Daemon Tools or other virtual drives.
