Vampires are re-animated corpses of people who have transformed into blood lusting creatures of the night. Though many theories and legends surround the story of the beginning vampirism, each culture has tailored to suit each societies location on the globe (very similar and antonymous to the theory of god/s in centered religions in different places). Some say that vampires are demons straight from the breast of the devil himself, sent to wreck havoc on earth, others believe that they are the awakened cadavers of those who died unbaptized. Chiefly they are not supposed to be physically able to venture into the light, lest it burn them to re-death. Their weaknesses are said to be garlic, the sun, holy or blessed things such as crusifixes and holy water, poppy seeds (though this myth died due to the easiness of destroying a vampire by spilling seeds onto the ground behind you, for he would have to obsessively count them until the sun came up), wooden stakes through the heart, decapitation, or being charred to ash with a flame.
Many vampire novels falsely depict vampires as recollective of their humanity, in becoming a vampire, one is set on a path to becoming a monster, once transformed, they permanently loose their soul and are bound to traverse the earth until they are killed a second time and cast into hell. They are renoun for either being breathtakingly beautiful, or horrifically disfigured. Either way they sat on the top of the food chain, practically impossible for animals to kill, and much stronger, faster, and clever than a mortal human.
The Cullen family in Stephenie Meyer's book Twilight was far from any of the original myths about vampires, nearly breaking every characteristic of the creatures. All of them had consciences and thought of others before their own needs, depicting souls which are non-existent once one is a vampire.
Lestat DeLioncourt on the other hand was a very convincing predator in the Vampire Chronicles by Anne Rice. He was cunning, quick, indulgent to himself, selfish, beautiful, and cultured (as would an over-one hundred year old being be).