What is mount loop in Linux? A “loop” device in Linux is an abstraction that lets you treat a file like a block device. It’s specifically meant for a use like your example, where you can mount a file containing a CD image and interact with the filesystem in it as if it were burned to a CD and placed in your drive.
What are loop mounts? Loop mounting has several uses. It is a convenient method for managing and editing file system images offline, that are later used for normal system operation. This includes CD or DVD images or installation systems. It may be used to install an operating system onto a file system without repartitioning a disk.
What is a Linux loop device? The loop device is a block device that maps its data blocks not to a physical device such as a hard disk or optical disk drive, but to the blocks of a regular file in a filesystem or to another block device.
How do I create a loop device in Linux? Creating a loop device
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS loop1 7:1 0 5G 0 loop  A typical case in which a loop device is automatically created on Linux, is when we mount an ISO file, like for example a distribution installer image (the iso file is mounted in read-only mode, of course):