Vellum is a type of paper made with inscription for use by enchanters to store enchants for later use. This allows for the trade and sale of enchantments without the enchanter and client meeting face-to-face. Prior to Patch 4.0.1, different types of vellum were needed depending on the level of the item to enchant or the type of enchantment; now, all enchantments can be applied to a single all-purpose [Enchanting Vellum]. The id for [Armor Vellum] was re-used for Enchanting Vellum and all other types became [Ruined Vellum].
Vellums can not enchant an item in the "will not be traded" slot of the trade window.
Vellums were designed to allow the enchanter to sell enchants via the auction house, mail them to their alts, or other characters on the same server and same faction.