Respectively, they are for the reduction (cutting to size), initial straightening, final straightening and smoothing of wood. They are called bench planes because they are most often used at a woodworking bench as opposed to on site.
Longer bench planes are generally used for straightening wood; shorter ones are usually used for smoothing.
Wooden Jack, Fore, Jointer and Smoothing Planes
As with most planes, there are wooden equivalents which are generally simpler in their design and construction.
Stanley Bailey Smoothing Planes
In practice, there’s some overlap between these planes. For instance, a jack plane might sometimes be employed as a smoothing plane, and vice versa.