The aperture controls the area of which light could enter the camera. People would say ” stopping down” or “opening up” because that’s the way they say when there going to increase it or decrease f-stop the lenses to say it polity. Shutter speed is when either the camera sensor will be opened or closed to the incoming light. The shutter speed is a tool for helping you freeze and show emotion. You can’t have shake hands because the shutter speed catches the motion. The ISO shows you have sensitive when light is incoming to the camera. ISO is commonly used increase because it will cause image noise. Camera exposure modes is the one that aperture, shutter speed, and ISO are chosen to given exposure.