The name is derivated from a norm issued by the International Organization for Standardization which specifies the file system on an optical medium . That norm has the abbreviation ISO 9660 and you can guess now why a CD-ROM image (and later on a DVD-ROM image) usually is named .iso.

An ISO image is an archive file of an optical disc, a type of disk image, composed of the data contents of every written sector of an optical disc, including the optical disc file system. ISO images can be created from optical discs by disk imaging software, or from a collection of files by optical disc authoring software, or from a different disk image file by means of conversion.

Once you have downloaded an .ISO file, there are three possible options you can use to install the software:

  1. Use .ISO image file software to download and save the .ISO image file to a CD-R or a DVD-R.
    Copy Image or Burn Image to CD using recommended burning tools.
  2. Virtually mount and access ISO files as a virtual device – recommended tools.
  3. Extract the .ISO files to your hard drive – recommended tools.

Related guides on how to use .ISO files: