What can vlc do

Play DVD/SVCD/VCD iso's / Images

If you have a DVD/SVCD/VCD packaged inside an image/iso file vlc can play this without you having to mount it or extract it in anyway. You can simply chose open file and pick the iso file. This is true for the standard .iso and .img files, not if its some proprietary format which is specific to a certain program (For example NERO's .nrg)