In basic photography terms, ISO is the photo sensitivity to available light. By changing the ISO, the lower the ISO number, the less sensitive the light is. while the higher the number of the ISO, the higher the increase of sensitivity to light.
This is the exposure triangle, over the course of a few weeks, I have learnt how to control shutter speed and aperture to produce a perfect photo. ISO would make up the exposure triangle which are the three elements a photographer needs to be aware of for a perfect photo.
This image shows the differences between different ISO numbers. The higher the number the more light is let in. Although, it makes the image more grainy. The lower the number on the ISO scale, the darker the image. Although, the image would show much clearer.
We did our own ISO shots and here are a few of our examples:
These are four of my sample shots. This is the same image changing the ISO from 6400 to 3200 then 800 and 100. The exposure to light is different making the images go darker as the exposure becomes less and less. The the more the camera is exposed to light, the brighter the image will be. However, the image also becomes more granulated the higher the number the IOS scale is.