What is an ISO image?

An ISO image refers to a complete copy of everything stored on a physical optical disk, such as a CD, DVD, or Blu-ray disc. This file is a single archive file that contains all the data and filesystem structure of the original disk, allowing for an exact replication of its contents. This is particularly useful for distributing large software packages, creating backups of optical disks, or for use in virtual machines where the media is not physically present.

The other options differ in their definitions and purposes. A software installation package typically contains the necessary files for installing software on a computer but does not serve as a complete disk image. A file compression format is designed to reduce the size of files for storage or transmission, but it does not replicate an entire disk's structure. Lastly, a type of hard drive refers to storage devices that hold data electronically but does not encompass the concept of an ISO image, which is specifically related to the contents of optical discs.