Wet lashes literally look like wet lashes, but usually longer and more pronounced than your natural lashes. However, I never go beyond what the natural lashes can carry, as "overloading" them can be detrimental to the natural lash.
To give the wet appearance, a closed fan, is attached to each natural eyelash. A wet set is thus essentially a volume set, but with less "fluff". They can be either natural or whispy.