NOTE: This is from hp-encyclopedia.com. I don't know what else to post.

There are many fantastical and amazing creatures in J.K. Rowling's Potterverse, and a multitude of them are drawn from, and inspired by, myth and folklore. One of the most famous creatures in folklore is the werewolf.

Word Origination and Meanings:
The modern usage of the word "werewolf" comes from Old English, "were" meaning man, and "wulf" meaning (obviously) wolf. Also, the term lycanthropy (the disease that is werewolfism) comes from the Greek language, "lykos" meaning wolf, and "anthropos" meaning human being. In Latin, "lupus" (presumably where the name Lupin was derived from) means wolf, and in mythology, Remus is a mythological figure who was taken care of as a baby by a mother wolf. According to Absolute Astronomy, there are a myriad of different names for the werewolf, each originating in a different culture:

Greece=lycanthropes (used in movies such as "An American Werewolf in Paris", and is also a term for the very real disease of lycanthropy.)
Spain =hombrelobo
Russia= volkodlak
France= loup-garou (also part of the title of a French werewolf movie, and a referring term to werewolves in "Werewolf: the Apocalypse" a very popular role playing game made by WhiteWolf)

Folklore:
As one can already see, there is in almost every culture, some kind of werewolf folklore passed down from one generation to the next. In Greece, the legend of the werewolf goes back to ancient times, concerning the King of all Greek Gods, Zeus. It is said that he masked himself as a peasant and went traveling far and wide. One of the places he happened upon was the court of King Lycaon in Arcadia. Lycaon was reputedly a vicious and violent man, but cunning and sharp witted as well. Almost immediately he caught on to Zeus's ruse and recognized him as a God. Lycaon then tried to feed Zeus human flesh for dinner as a kind of cruel and disgusting joke. Zeus, being a God, recognized the strange meat for what it was and punished Lycaon by transforming him into a wolf that, in some stories, preferred human flesh above all other prey. The evil King's name, Lycaon, is supposedly where the term lycanthropy originally came from. A modern campfire version of this story tells of a man who vehemently refuses to eat meat. His wife, (or friend, daughter, son, etc. depending on the storyteller) eventually gets frustrated with this refusal, and slips a small amount of meat into his vegetable stew. He then proceeds to devour the stew enthusiastically, slowly transforming into a werewolf. Once fully transformed, he flees, never to be seen again. In some versions of the story, he devours not only the stew, but also his wife. In many folkloric legends, a werewolf craves human flesh above all others. (As a side note, many, if not most, campfire stories and urban legends are based in folklore.)

In England, America, France, Romania, Greece, and a host of other countries, the folklore of werewolves is very similar. You can become a werewolf in numerous ways, the most popular theory being that you can become one if you are bitten by a transformed werewolf. Some other folkloric theories and ways to become a werewolf are: if you are born under a new moon or a full moon, if you were born with a caul (a fetal membrane covering the face at birth), if you sleep outside during the full moon, if you are cursed by a gypsy, form a pact with the devil, or by being a cannibal. In J.K Rowling's epic tale, the character Remus Lupin is bitten at a very young age by a werewolf.

In some folklore, a person who is a werewolf will transform only at the full moon, and will not have any rational human control over his bestial form. In other stories, such as some Native American folklore, the werewolf can transform at will, though usually at night. This is also true of people who have made pacts with the devil (although, it is highly doubtful that many people made "pacts with the devil". This seems to be a largely used excuse made by the strictly religious people of the time to persecute anyone that was different, or to persecute anyone who not liked by the general community. If you would like a great example of this strict religious hysteria, read The Crucible, by Arthur Miller. ) At any rate, the character of Remus Lupin is stated to transform at the full moon only, and not at will. As with general folklore, he does not have any control over himself in this state. He would kill anyone or anything in his fearsome fully transformed lycanthropic state. In some stories, there is a kind of "lycanthropic cycle", where the werewolf in question becomes more and more powerful (such as in heightened senses) as the full moon approaches, but also more out-of-sorts, confused, and emotionally vulnerable…meaning that the "wolf side" of the personality is beginning to upset the balance and dominate over the human side. (Two great examples of this kind of werewolf can be seen in the book Cycle of the Werewolf, by Stephen King, and the movie "An American Werewolf in Paris") In the Harry Potter series, this kind of cycle seems to be mildly suggested by way of Remus Lupin's appearance of sickliness before and after the full moon. The fact that Lupin actually suffers from a kind of "lycanthropic cycle" is not verified, but seems likely.

Can you be cured of werewolfism? In J.K. Rowling's story you cannot be cured, but the disease can be controlled by imbibing Wolfsbane Potion. It is not clear if this potion completely halts any transformation, or if it just lessens the severity of the transformation somehow. In Prisoner of Azkaban, Lupin has been taking the Wolfsbane Potion, but he still turns into a werewolf; did he forget the potion, or is it as the Harry Potter Lexicon suggests, that with the help of the potion, he only transforms when the "moonlight actually strikes him"? In some folklore, particularly Eastern European, you can sometimes be cured by a gypsy or priest. In other tales, such as some Native American and American stories, you can be cured by killing the wolf that bit you.

Lastly, what kills or defeats a werewolf? In folklore, there seem to be two camps---those stories that state that you can vanquish, or cure, werewolfism somehow (see above paragraph), and those stories that state that there is no cure except for the death of said werewolf. In my research, I have only seen two ways to actually kill a werewolf---burning them at the stake, or silver weaponry of some kind (bullets, spears, swords, etc.). This brings up an interesting observation concerning the Harry Potter series. At the end of Goblet of Fire, the dark wizard Voldemort gives Peter Pettigrew a silver hand in return for Pettigrew cutting off his own human hand for use in a terrible rebirthing-type potion. In the HP series it is not yet stated if werewolves are vulnerable to silver---but if that is the case, then it would be very wise indeed to watch out for Pettigrew. Remus Lupin and Peter Pettigrew are not only enemies, but the last of the 4 Marauders. They may just turn out to be each others' arch nemeses, but at this point, it all remains speculation until we confirm (or do not confirm) that J.K. Rowling's version of werewolves are vulnerable to silver.

Some History:
In the 14th - 16th centuries, in England, France, Romania, and many other countries, the fear of werewolves grew to a fever pitch, inciting not only religious riots, but also the stake burnings of many people under the suspicion of werewolfism. This was also the time of witch hunts and burnings, and an unusually religiously strict time in history. This was the transition period between the Middle Ages (or the Dark Ages, Medieval, etc.) and the Renaissance (the precursory age to modern times). As a world, we were coming out of a time when religion and magic ruled the Earth, and into a time where science and rational thought prevailed. During this transition, a very strict form of Christianity asserted itself, and anyone who was not Christian, did not conform to the normalcy of society, or was different in any way, was in great danger of being labeled a witch, werewolf, vampire, or consort of Satan.

Lycanthropy:
Lycanthropy is a very real disease; it is a severe mental disorder in which the patient believes he or she has transformed into a wolf or werewolf. It is characterized mostly by violent, animalistic outbursts, and the adrenaline pumping through the body's network of systems during such an outburst, can give the sufferer a temporary boost of physical strength, and a heightening of the senses. This disease is usually governed by the moon's cycles. It is an absolute fact that the full moon has an effect on human behavior…just ask any police officer or emergency room nurse what full moon nights are like. Also, words like "lunacy" and "lunatic" were originally coined from the effect the full moon has on one's behavior. The word "luna" or variations of it, ( like "lunar" in English) mean "moon" in a few languages. (These facts are very interesting to note in another character, Luna Lovegood. She is considered a "loony" and portrayed as very strange. Well her name suits her, apparently)

Traditional Werewolf?
By most standards, Remus Lupin is, so far, a pretty traditional example of a werewolf. He was bitten by a werewolf as a child, and therefore turned into a werewolf himself. He transforms into a werewolf at the full moon. He is entirely terrifying, vicious, and unaware of his human side while in his lycanthropic state. It is mildly suggested that his biorhythms adhere to some kind of lunar based lycanthropic cycle, though this is not confirmed. There seems to be no cure for his condition. There is only one traditional aspect that has not yet been covered by J.K. Rowling…vulnerability to silver, or any way in which to kill a werewolf. In Prisoner of Azkaban, Professor Snape assigns an essay about werewolves with particular emphasis on ways to recognize and kill it. But for we as readers, it never goes beyond that---the question of how to kill a werewolf remains unanswered. This particular question looms over us ominously as the second Wizarding War gets into full swing… and the more we study werewolf folklore for clues and answers, the more sinister Pettigrew's new silver hand becomes. At any rate, Remus Lupin is a seemingly very traditional werewolf, and wherever the story of this particular character leads us, it is sure to be interesting…especially when the full moon glows bright overhead in the night sky.