ISO does not affect the exposure of our image because it doesn't control the amount of light hitting our digital sensor.
When we shoot film, we can use film with different ISO ratings that are a measure of the sensitivity of that film to light. A low ISO film is less sensitive than a high ISO film.
Digital sensors are not the same although it is easier if we think of digital ISO in the same way.
In this course you will learn the truth about ISO and one of the reasons why the "exposure triangle" is misleading in teaching us about exposing our images.
You will also learn how I use ISO in my daily photography so that you can be more aware of the choices you have in creating great photographs.
As with all of my photography courses, I can give you my opinions (based on 40 years in the photographic industry) but ultimately I want you to make your decisions based on what works best for you. Listen to people who know what they are talking about, test their advice and see the results. Then you can move forward knowing the facts.

https://www.skillshare.com/classes/Understand-ISO-It-is-not-really-what-you-think-it-is/1531485518