Aperture

Aperture is the size of the hole or "pupil" of the camera. the difference in sizes determines the focus of the subject and background. the smaller the hole, the wider the shot. the picture on top is an example of a small aperture with a higher F-stop because with a smaller hole, less light comes in to blur the picture giving the photographer a high depth of field. the bottom picture is an example of a bigger aperture with a smaller F-stop, bigger hole means more light comes in and blurs much of the background but gives the photographer a macro shot.