Anyone who has spent time burning data to discs has dealt with ISO files. An ISO file is basically a copy of an optical disc. The 'ISO' refers to the International Organization for Standardization. ISO developed a specific standard ISO 9660 which allows different operating systems to exchange data. ISO files don't use the first 32 KB of a disc - this is referred to as the system area. This is reserved for data that consists of alternate file system descriptors. The beginning of the data area is followed by a volume descriptor set of 2 KB. This is in effect the header of the data, and always begins with 'CD001'.
An ISO file can be opened with file extraction software like 7-Zip.
ISO 9660 can only support files of more than 4 GB on DVDs with a fragmentation feature. Mac OS devices may not be able to deal with these fragmented files.