The silver greatsword's inherent effect increases its damage by 20 points when used against undead such as draugr, skeletons, dragon priests, vampires and re-animated corpses. Despite not being undead, werewolves and werebears are also affected.
The effect is not a normal enchantment, so it is affected by the Elemental Fury shout and silver greatswords may be enchanted at an arcane enchanter to stack with its inherent ability. The description "Especially effective against Undead" will remain. The silver greatword cannot be crafted or upgraded at a grindstone. [Source: wikia]
You can download the papercraft model here: The Elder Scrolls V: Skyrim - Silver Greatsword Free Papercraft Download