Shutter speed determines when the camera sensor will open or close to light coming in from the camera lens. Shutter speed is what allows the light to enter and for how long to enter. Faster shutter speed means shorter exposure time.

Aperture is what controls the light. It controls where the light can pass through on your camera.

Iso speed is when the camera determines how sensitive it is to incoming light. Similar to shutter speed it also correlates with how much the exposure decreases or increases. However, it Is a lower ISO speed.

Exposure determines how light or dark an image will appear when it has been captured.