Aperture.

Aperture is 'the hole' in which the camera lets light in, by changing the aperture it changes the size of the whole is, thus changing how much light the camera is letting into the image. The smaller the F-number the bigger the hole will be and the greater the F-number the smaller the hole will be. F-stops also change the depth of field on a camera, by using a shallow depth of field the photographer is able to get less of the image in focus thus being able to put more attention on smaller details of the picture which is always good for doing portrait shots and still life. Having a wide depth of field means that more of the picture or even all of the image will be in focus, this is better for doing landscape shots.

Deep depth of field;

shallow depth of field;