I found this in the official manual on the official forums:
Line infantry was the most common Infantry type in the
Napolenic wars. Line infantry are usally equipped with a bayoneted
musket and sometimes with a small sword referred to as a “butter
knife” or “sabre briquet”. Line infantry have medium shooting and
melee skills and are a good all rounder troop type.
Light infantry are light and fast moving units that possess good
shooting skills. Light Infantry is equipped with an unbayoneted musket
and a small sword for melee combat. Due to their good speed and accuracy; they are
especially useful for flanking enemy lines and supporting fire.
However, light infantry is at a disadvantage in melee and should thus
avoid getting to close to enemy lines.
Riflemen and Jaegers
Riflemen are light and fast moving units with good shooting skills. Riflemen
are equipped with a highly accurate but slow to reload rifle and a
small sword for melee combat.
Due to their high shooting and running skills, riflemen are especially useful for sniping enemy officers. However, Riflemen are at a strong disadvantage in melee combat and should avoid getting close to enemy lines.