Aperture
Aperture is measured in f stops and it determines the amount of picture that is being show for example if you want everything in the photo you would use a large f stop like f22 which would be a narrow opening and it would be referred as a deep depth of field where as a wide opening would be called a shallow depth of field and it would be a small f stop.The aperture stop of a photograph can be adjusted to control the amount of light reaching the image. It works with shutter speed and the aperture. A fast shutter will require a larger aperture to ensure a high light exposure, and a slow shutter will require a smaller aperture to avoid images being over exposed.The lens aperture is usually specified as an f-number. A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number creates a greater aperture opening which allows more light to reach the image.