File type: Disk Image Files
ISO file is an image format for copying and storing CDs or DVDs on the hard disk. This format is based on ISO-9660 standard and contains the exact replica of the data on a disc. This is used for making copies of the CDs or DVDs and to store it on the hard disk.
These files include the data that was saved on the disc as well as all the details such as the filesystem information of that disc, its complete directory structure, the attributes of the files as well as the boot code so it can be used as a boot disc if the appropriate code is there.
These files can also be mounted over virtual drives and then browsed and viewed just like the physical discs whose copies they were. ISO files are also used for making backups of CDs or DVDs since the physical discs have a limited lifetime and deteriorate gradually.
This is a binary format in that it copies the entire contents of the CD or DVD bit by bit exactly as it was on the disc which is different from manually copying all the files from a disc to the fs as that would not be able to copy the discs header data which contains the information regarding the filesystem of the media and other relevant details.
They can be used to copy the data of one CD or DVD onto another empty CD or DVD using a DVD Writer and a DVD burning software.