Aperture

Apertures (aka f-stops) are expressed as a fraction.  (I remind people of this concept to help them remember that f/2 provides a much larger opening (aperture) than f/16.  For example, 1/2 is significantly more than 1/16^th.)  The larger the aperture, the less depth of field; the smaller the aperture, the more depth of field.

However, in terms of light required, the aperture is the inverse of shutter speed.  In other words, the smaller the aperture, the longer the shutter speed.

But aperture is more than just light.  Aperture affects “depth of field”.  I use the example of surface appeal.  If the surface is completely flat, f/11 at ½ second may provide optimum results.  If the impression is on a curved or irregular surface such as a pop can, doorknob, battery, light bulb, or screwdriver, you must use a smaller aperture (such as f/22) for maximum depth of field.