Definition: This is the number assigned to determine the aperture, or size of the lens opening. A high f-stop number means a small amount of light is allowed in, which would be used to avoid an overexposed image. A low f-stop number means a large amount of light is let in, as you might use to shoot at a high shutter speed without getting a dark image.
Examples: I used a high f-stop setting to avoid my image being too bright and sunwashed.
