An aperture is what controls the area over which light can enter your camera and it is a setting controls the area over which light can pass through your camera lens. Shutter speed controls the duration of the exposure and Also a camera’s shutter determines when the camera sensor will be open or closed to incoming light from the camera lens. ISO controls the sensitivity of your camera’s sensor to a given amount of light and it determines how sensitive the camera is to incoming light. Similar to shutter speed, it also correlates 1:1 with how much the exposure increases or decreases.