Giles: For as long as there have been vampires, there has been the Slayer. One girl in all the world, a Chosen One… Buffy: He loves doing this part. Giles: Alright. The Slayer hunts vampires, Buffy is a Slayer, don’t tell anyone. Well, I think that’s all the vampire information you need.
Yes, it’s terribly simple. The good guys are always stalwart and true, the bad guys are easily distinguished by their pointy horns or black hats, and, uh, we always defeat them and save the day. No one ever dies, and everybody lives happily ever after.