Progressives are sometimes referred to as "no-line bifocals", "no-line trifocals", or "vari-focals." They provide a graduated range of vision from distance to near, without a line.
Bifocals have 2 focal points, one for near, one for far.
The progressive lens gives you the intermediate distance also that a bifocal can't do.
The reading area of a bifocal is always going to be wider than in a progressive, and the distance porion of the lens is normally clear right to the outer edge of the lens.
With the bifocal, if you are standing at a desk, you can't read a note on the desk without picking it up to bring it within the fixed focal distance of your reading segment.
With the progressive, you can, because you have the intermediate power also to be able to focus at any distance.
Most progressives will blur out at some point on the outer edges of the lens in the distance portion, however the brain gets used to that and it doesn't bother most people for long.
Truck drivers have trouble with progressives because of that, with the side mirrors they have to glance at all the time on both sides.
The reading area of the progressives is also narrower than with a regular bifocal, therefore you have to move your head more, not just your eyes to read across an open newspaper.
If this is going to be your first time wearing either, then the progressive is the best way to start. Once you get used to it, it is more like normal vision because of that intermediate portion.
Progressives take a good 2 weeks to really feel at home in, but 95 % of those who have them wouldn't switch.