In the fictional world of the television series Buffy the Vampire Slayer and Angel, a vampire is a species of demon which inhabits and animates a human corpse. In Fray, a Buffy comic book spin-off, vampires are also called lurks.
The vampires in the canonical Buffyverse differ greatly from the ones which appear in the 1992 Buffy the Vampire Slayer movie. The non-canonical vampires are able to fly, look pale but relatively human, and don't crumble to dust when killed. On the other hand, the canonical vampires, introduced in the first episode of the TV series, are explained as demons inhabiting human corpses; when the ancient demons known as the Old Ones were banished from Earth, the last one fed on a human and mixed their blood, creating the first vampire. This was later contradicted by Illyria who remarks that vampires existed during her time as an Old One, long before the rest were banished from the realm (though she may have been referring to the Turok Hans, the prehistoric vampires).
Vampires possess supernatural physical abilities such as enhanced strength, agility, hearing, smell, and healing. They do not require oxygen, food, or water, but live on a diet of blood; prolonged periods of time without consuming blood can have an adverse affect on a vampire's higher brain functions and they become "living skeletons". Vampires can change at will between human appearance and a monstrous form with a bumpy forehead, yellow eyes, and sharp teeth. In human form, they can still be detected by their lack of heartbeat and body heat. Vampires cannot be killed except by beheading, fire, or penetration of the heart by a wooden object. They heal quickly from most injuries, but do not regrow lost limbs. Their flesh burns in direct sunlight, and on contact with blessed objects such as holy water, recently consecrated ground, or a Cross. They can enter consecrated buildings but appear to feel ill at ease. They cannot enter a human residence without invitation and do not cast reflections, although they can be photographed and filmed. In the Buffy season three episode "Earshot", it is revealed that their inability to cast reflections also extends to their minds; when Buffy is temporarily endowed with telepathic abilities she cannot read Angel's thoughts. A vampire explodes in a cloud of dust when killed; the act of slaying a vampire is often referred to as "dusting" on the show.
In order to reproduce, a vampire must drain a human being of much of their blood, before forcing them to drink some of the vampire's blood. This process is known as "siring", and the vampire which does so is referred to as the newborn vampire's "sire" (along with the vampire which sired the sire, etc). The amount of time it takes for a new vampire to rise seems to vary; Buffy often kills vampires as they rise from their graves, but other vampires are seen to rise after only a few hours. There is no explanation given for this in the series. A sire will often act as a mentor to their 'children' and form small covens of related vampires for various reasons. Vampires can't normally reproduce through sexual intercourse, but in season four of Angel, Jasmine manipulated events that allowed Angel and Darla to conceive a human son, Connor.
It is regularly established on the show that vampires do not have souls and therefore lack a conscience. Angel and Spike, vampires who have their souls returned to them, are shown to feel remorse for their previous actions.
Variations of vampires are seen on both Buffy and Angel. In the Angel season two episode "Through the Looking Glass", Angel and his team travel to a parallel world, Pylea. Here he is not harmed by sunlight, but when he attempts to take "vamp face", he instead becomes a "Van-Tal" demon: green-skinned, spiny and bestial. In Buffy's seventh and final television season, Buffy encounters the Turok-Han - an ancient species of vampire analogous to Neanderthal man. These Turok-Han, colloquially referred to as "über vamps" by the characters, are stronger and harder to kill than regular vampires, able to withstand a stake to the chest without dusting; but like the Van-Tal of Pylea, they show little intelligence and are incapable of language.
The idea of the "vamp faces" — to have vampires' human features distort to become more demonic — was implemented for a number of reasons. Firstly, Whedon wanted normal high school students that the other characters could interact with normally, only to have them turn out be vampires, therefore creating a sense of paranoia. Secondly, he was conscious to make the vampires look physically demonic, claiming, "I didn't think I really wanted to put a show on the air about a high school girl who was stabbing normal-looking people in the heart. I thought somehow that might send the wrong message, but when they are clearly monsters, it takes it to a level of fantasy that is safer."
In early episodes, the vampires appeared "very white-faced, very creepy, very ghoulish". This was changed in later seasons to make the vampires look more human, partially because of the sympathetic vampire character Angel, and partially because such elaborate make-up was too time-consuming. Whedon claims that people thought the white faces to be "funny looking" but personally found it creepier, comparing it to the monsters in zombie movies such as Day of the Dead and The Evil Dead. The character of the Master was designed to be in vamp face permanently to highlight his age and make him appear more animalistic; make-up artist John Vulich based the Master's appearance on a bat, reasoning that the character has devolved to a more primal, demonic state over the years.
It was decided that vampires and their clothes would turn to dust after they died because it was more convenient storywise; Whedon wished that the supernatural elements of the show to remain somewhat hidden from the normal world, without devoting time in each episode to "let's clean up the bodies" after Buffy slays a vampire. Indeed, the introduction to one episode, The Wish, parodied this vampiric trait; when Buffy kills a non-humanoid demon, one of her friends, Willow, wonders why the demon corpse "doesn't go poof" and must be buried.
The first episode toyed with the idea that vampires' clothes would resemble the era in which they died, with Buffy identifying one purely by his dated outfit. Joss Whedon felt this concept was a "charming notion" but ultimately rejected it for the most part because he believed that if every vampire in the show was dressed in old-fashioned clothes, they would cease to be scary.
When creating the vampire "rules" that they would use in the show, the writers chose bits and pieces from various existing vampire lore. They decided not to have the vampires fly as in the Buffy movie because it was impossible to make flying vampires look convincing on a television budget. Some established rules, such as a vampire's inability to enter a home uninvited, both helped and hindered the storytelling. Joss Whedon says that, whereas shows such as The X-Files spend more time explaining the science behind the supernatural and making it as real as possible, Buffy and Angel are more concerned with the emotion resulting from these creatures and events than justifying how they could conceivably exist. As such, the shows tends to gloss over the details of vampire and demon lore, simply using the Hellmouth as a plot device to explain unexplainable things.