From Abracadabra to Zombies
In a nutshell: A werewolf is a mythical creature who is a sort of hybrid, part wolf and part human.
A werewolf is a monster from folk stories that can change from human to wolf and back again. The werewolf eats human flesh and drinks human blood. While there are no proven cases of any human turning into a wolf, there have been a few humans who believed they were werewolves. It's possible that the legend of the werewolf was fueled by people ignorant of certain diseases (such as hypertrichosis) that can cause a person to become very hairy.
Before Charles Darwin's theory of evolution, the idea of a creature that was half-wolf and half-human was a popular one in folk stories. Many people believed werewolves were real and hiding behind every tree in the forest, waiting to pounce on travelers. The history of evolution makes the idea of such a hybrid creature seem silly. Wolves are part of the canine family and humans are part of the ape family. Both families branched off from a common ancestor so long ago that no scientist today would think of looking for a fossil of something like a werewolf.