The file is called an ISO file because it conforms to the ISO-9660 standard (probably with ‘Rock Ridge Extensions’ but you don’t care about that and neither do I). ‘ISO file’ is just a way of describing the format of the data in the file. It’s actually a complete filesystem encapsulated in a file. If you want to see what’s in the filesystem you can mount it on a Linux machine with something like

mount -t iso-9660 -o loop imagefilename /mount/point/

then you can cd into the newly mounted filesystem and play around.

To use t as intended all you have to do is use a CD or DVD burning program to write the file to an optical disc. It is a ‘bootable image’ so if your computer can boot from the CD or DVD drive it will be able to boot from the image you write to the disc, assuming (a) it’s written properly, (b) your computer hardware is more or less a PC, not something odd (e.g. a Macintosh) and (c) most of the computer hardware is working properly.

This will not ‘repair’ a hard disc of the hard disc is actually broken. All it does is tidy up the software on the disc – assuming that the disc itself is working properly.

I don’t know if booting from this ISO image will work if you write it to a flash device like a USB stick but I doubt it. I’ll probably give it a try and report back.