One of the filesystem types known to Linux is ISO-9660. Very often, a filesystem image of type ISO-9660 is used as a vehicle to transport a complete partition. Such image files are, by convention, named with the .ISO (or .iso) filename suffix. Generally, an ISO image can be burned to a CD or DVD directly, in order to create media with a full ISO-9660 filesystem. This is a standard method used to distribute Linux through the internet. LQ has a considerable volume of information
on this subject.
Linux also has the interesting capability of being able to mount a filesystem image file (an ISO file) on a loop device
. Doing so allows you to access the contents of the ISO image as a mounted filesytem; you can browse the files and directory structure just as you would do on a spinning media filesystem.