When most people think of werewolves, they think of half-man, half-wolf creatures that walk around on two legs, are 'allergic' to silver, and, well, eat people. However, this is not necessarily the case, though a bite does actually turn a person. I believe that there are several types of werewolves/possiblities of what werewolves are.
1. The Recessive Werewolf: This type of werewolf has normal, human parents with werewolf genes in their blood. These genes just happen to be passed down to their child, who, obviously, becomes a werewolf. You would think this would make them weaker than purebreds, but it actually makes them twice as strong. These individuals can often be dysfunctional and angry, but with the proper self-control, they can make great leaders. Just like the Pureblood werewolves in body type.
2. Pureblood Werewolf: This is the second strongest type of werewolf. They are born from a line of pureblood werewolves, meaning that they have no human/vampire/whatever blood in them. When in wolf form, they are just bigger versions of wolves, and much stronger.
3. Halfblood Werewolf: This werewolf has been either bitten by another halfblood or born from a human and a werewolf. Either way, they are almost as strong or just as strong as pureblood werewolves. They may or may not be able to control themselves, depending on the individual. Same body structure as purebloods.
4. Strigoi: Some people say strigoi are vampires, others think differently. (Obviously, I am one of those few ^^) A strigoi, or whatever you want to call it, is where you get creatures like Lupin from Harry Potter and the Prisoner of Azkaban, or the hollywood version. These are creatures are people who had a vendetta against someone during their life, and when they died, they couldn't let go. So they came back like the vampires do (sort of) and live as a werewolf-like creatures until either the person they have something against dies or the vendetta is fulfilled in some way. Other people refer to them as 'lycans', though, technically, I'm pretty sure that's a disease otherwise known as 'lycanthropy.'