Shutter Speed:In a camera, the shutter blocks all light from exposing the film UNTIL you press the button. Then it quickly opens and closes, giving the film a brief flash of light. You can control the length of time the shutter remains open by setting the SHUTTER SPEED.
Aperture: When light passes through a camera's lens, it must pass through an opening called an "Aperture". In plain English it's a hole that lets in more light when it's wide open and less when it's small. In essence the aperture is just like the pupil in the human eye. You can control the aperture by setting the "Aperture Opening", also known as an F-Stop.
ISO: ISO is the sensitivity of light. The lower the ISO is the less the noise/ grain is. On the other hand the higher the ISO is the more the noise/grain is.
