It is a disk image.
You would have to use some software to “mount” that image, after which you will see it as if you had inserted a disk with the software you were downloading.
An ISO is an image of a CD or DVD. Most every CD burning software can take an ISO and burn a CD or DVD from it. If you want to mount the ISO so you can read from it just like it’s a CD you’ll need something like Magic ISO or Virtual Clone Drive. If you just want to extract the files from the ISO then you’ll want something like ISO Buster.