ISO and Exposure

Technically, Iso is not part of exposure. Shutter Speed and aperture brighten your photo by physically capturing more light

ISO doesn't do that: instead it essentially brightens or darkens the image

ISO SETTINGS & SPEEDS

As you increase your ISO number, your photos will grow progressively brighter.

When you double your ISO speed you are doubling the brightness.

however raising your ISO has consequences and a photo taken at too Hugh of an ISO will show a lot of grain, also known as noise

ISO low vs high

The lowest ISO on your camera is your BASE ISO, this is a very important setting because it gives you the potential to produce the highest image quality.
The base ISO is generally 100 ISO

When you are fighting against motion blur, you will need to pick between a sharp photo at a high ISO, or a blurry photo at a low ISO

If you use a slow shutter speed or wide aperture to brighten a photo when photographing a fast moving object then it will be blurry meaning you will need a high ISO to brighten the image.