Wyverns are a type of dragon-like monster that have originated in various medieval folktales. The most note notable distinction being that wyverns have only four limbs for legs and wings while their cousin race dragons have six limbs for arms, legs and wings. They have since then become a very iconic creature in various modern fantasy stories.
Wyverns have existed since roughly 752 AD in medieval times, with depictions ranging from the Golden Dragon on the Flag of the Kingdom of Wessex to other more obscure refrences of two-legged dragons during a span of several centuries. The word wyvern itself originated as wyver which in turn is derived from wyvere which means vipers and or life in French. Wyverns have since then been seen as a symbol of war, envy, pestilence and even strength to those who bear it in medieval heraldry.
Wyvern are characterized by having only four limbs for legs and wings as suppose to dragons who have arms legs and wings. Wyverns are also far less intellegent compare to their said cousin race, being depicted as feral beasts that only kill to ensure thier survival, a stark contrast to dragons who are often seen as malicous monsters that kill millions to satisfy their bloodlust. In various folktales wyverns are stated to have very little if not no magic at all they also lack any form of fire breath with the exception of more modern interpretations. To make up their shortcomings, they rely more on brute strength and agility to gain an edge on their oppenents. Thier most notable weapon being their bladed/barbed tail which, depending on the species, contains a deadly venom potent enough to kill a person within minutes. For long-range attack, some displayed the ability to spray acidic venom from their mouth. All of these skills make wyverns very dangerous foes to face.
Wyverns have since then become one of the most iconic monsters in modern fantasy, even in fantasy stories where wyverns don't exist there are still dragons that posses wyvern-like traits but are not refered to as wyverns, such as the dragons from The Elder Scrolls, Game of Thrones, The Hobbit, and Drakengard, among various others. In settings where they do exist, wyverns are characterized as either a less intelligent sub-species of dragon, a different breed of dragon, or an entirely different creature all together. Wyverns are especially common in RPGs serving as super strong enemies and even bosses. As villains, wyverns have often been depicted viciouse beasts that often serve a higher power, such as in Monster Hunter (where they are the most common type of creature faced), Fire Emblem (where they serve as war mounts by the more villanous kingdoms such as Macedon and Bern), and The Lord of the Rings (Where wyvern-like creatures known as Fellbeasts are ridden by the Nazgûl). Thou they are not always antagonistic and villanous, some wyverns are depicted as neutral in nature, or even benevolent, willing to fight along side humans against evil. thou whether they are decpicted as being good or evil lies solely on the author's interpretation.