Bifocal lenses offers two different viewing zones: the top part of the lens is for distance (i.e. to help you see things far away) and the lower part for the lens is for reading (i.e. to help you see things up close). The viewing zones of bi-focal lenses are divided by a visible line.
Progressive lenses are essentially no-line as bi-focals. But instead of offering just two different viewing zones (near and far vision), progressive lenses offer many different focal points by seamlessly transitioning from distance vision to intermediate and near vision and everything in between. Progressive lenses provide much more natural vision and are typically recommended over bi-focal lenses.
