As Spryfly stated an iso file is an image of a CD/DVD. To view it on a PC you either burn it to a CD/DVD (basically depends on it's size ) or mount it on a virtual drive. A virtual drive is just a way of being able to play a CD or DVD without actually having the physical CD or DVD.
If you use a product like Daemon Tools ( http://www.daemon-tools.cc/dtcc/portal/portal.php ) it will create a virtual drive on which you can mount your iso image & pretend that it's a real CD/DVD. This way you can install software , play a DVD etc using just the iso file.
Whether you can get an iso file onto your computer is another matter.
I hope that makes it fairly clear.