Progressive lenses are also called no-line bifocals sometimes. progressive glasses allow you to see at all distances from far to near including the arm's length for computer use. Unlike the bifocal glasses which provide two parts of powers, progressive glasses provide many lens powers, which allow you see everything in different directions. If you wear progressive glasses, you don't have to move your head up and down to find the correct area to see through the lenses. You will feel more comfortable to wear progressive glasses.
progressive glasses also considered as varifocal eyeglasses. A pair of progressive lenses can contain three different eye prescriptions so give you comfortable vision at all distance, far, near and mide area. Since the lenses provide three focus that allow it made with three different prescription, thus to correct vision for different distances for people who have more than one vision problems.
Progressive lenses provide bifocal vision correction, but with no visible lines! Lined Bifocals have a distinct line or etch in the lens which visibly indicates where the lens switches from reading to distance vision. Progressive lenses are able to complete the transition between the vision corrections smoothly; letting your eyes naturally move between reading and distance vision without the distracting line in your lenses.