Progressive lenses, which are also referred to as multi-focals, are lenses that correct for Presbyopia; a condition that is caused by the aging of the eye and its inability to focus on close objects.
Progressive lenses allow the individual to wear their glasses all the time and see everything they need to, regardless of the distance of the object from the observer. This makes them much more convenient than conventional readers.
No two people are exactly the same, their vision needs, lifestyles and prescriptions make it so that one type of progressive does not work for everyone and every situation. Nikon has a wide variety of progressives to help.