An ISO image or .iso (International Organization for Standardization) file is an archive file that contains a disk image called ISO 9660 file system format. Every ISO file have .ISO extension has defined format name taken from the ISO 9660 file system and specially used with CD/DVD rom’s. In simple words an iso file is a disk image.
ISO images can be created from optical discs by disk imaging software, or from a collection of files by optical disc authoring software, or from a different disk image file by means of conversion. Software distributed on bootable discs is often available for download in ISO image format. And like any other ISO image, it may be written to an optical disc such as CD or DVD.
Mount an ISO image:
root# mount -t iso9660 -o loop /root/debian-8.2.0-amd64-xfce-CD-1.iso /mnt/iso/
Unmount an ISO image:
root# umount /mnt/iso