In photography, aperture refers to the adjustable opening in a camera lens through which light passes to reach the image sensor or film. Measured in F or T-stops, the aperture size controls the amount of light entering the camera, influencing exposure and depth of field. A lower f-stop (wider aperture) allows more light and produces a shallower depth of field, ideal for emphasizing a subject against a blurred background, while a higher f-stop (narrower aperture) results in greater depth of field, keeping more elements in focus.