ISO files are disk images. A complete copy of a CD or DVD disc in one file. This file can be "mounted" and accessed as a virtual CD or DVD available as a physical disc.
Let's learn how to create disk images.
In Linux you can create an ISO image using the terminal or the burning software included in your distribution. For example, in Linux Mint ISO image can be created using utility, Brasero. To do this, open Brasero, select Disk copy and select the Disc to write to. The image will be created. In other distributions include other programs, but the essence remains the same - copy a physical disk to the image.
Clicking on the Properties button, you can choose where to save the image and can also choose the format for the generated image.
Also, you can create an image with the command in the terminal:
sudo dd if=/dev/cdrom of=/home/username/image.iso
Replace /dev/cdrom with the path to your optical drive, e.g. /dev/dvd and /home/username/cd.iso — the path to the future ISO image.
The resulting disk can be mounted by the mount command, right there in the terminal or with the graphical tool to choose according to your taste.