The vampires in the Twilight series have certain distinctive characteristics that set them apart from other fictional vampires, some of which include appearance and hunting styles.
Vampires are normally extremely beautiful, and their skin is described as extremely cold and as hard as granite, and is often compared to alabaster. Their scent is very appealing to humans who get close enough to smell them. Vampire eyes start out as a crimson red; a red eye color indicates that a vampire is either a newborn or has recently consumed human blood. The color becomes onyx black when a vampire is in need of blood. However when a vampire's eyes are a golden color, it indicates that a vampire has instead consumed animal blood. Their irises fade in color as time passes after their feedings. Purplish-black bruises appear under their eyes, becoming more pronounced with thirst. The bruises signify the fact that vampires never sleep. They are extremely pale, but flush slightly after feeding. Their skin also sparkles like diamonds once exposed to the sun, but apparently not while exposed to artificial light sources for reasons not explained, giving them the reason to never show themselves in public when the sun is out and uncovered by clouds. They do not need to breathe, however they generally do out of habit and because they feel uncomfortable without their sense of smell. They are also unable to sleep, age, or grow.
A vampire's eyes color changes with their diet, whether they drink human or animal blood. Hence, the Cullens all share "liquid topaz" eyes. The Cullens have all fed on animal blood for so long, that their eyes have become this golden color. Bella first notices Edward's eyes in Twilight, saying that "His eyes were black, coal black." This was because as a vampire gets thirstier, their eyes grow darker. Edward was so thirsty at the time, his eyes had gone as dark as they could: black. Why he was allowed to leave the house is anyones guess. In contrast, as a vampire drinks more blood, their eyes become lighter.
If a vampire was to have a diet that consisted entirely of human blood, their eyes would be a vivid red, like that of James and Victoria. Like the vegetarian vampires, their eyes grow to a more vivid red as they feed on human blood, and a darker, more burgundy color as they abstain from human blood.
Meyer writes that, "If a Cullen were to drink human blood, his/her eyes would turn burgundy. If two weeks pass without human or animal blood the vampire's eyes go entirely black. If that Cullen then returned to an animal diet, his/her eyes would return to dark gold. Brand-newly created vampires are recognizable by their eyes, which are a vivid, bright red due to the massive amount of human blood (the blood that was already in the human at the time he/she was changed) that lingers in the tissues. That red fades slowly over the course of a year."
Once a human completes the transformation to become a vampire, they acquire certain superhuman abilities; speed is one of these. The speed at which a vampire can move and be fast enough, that the human eye can barely recognize when a vampire decides to move at such high speeds. It is implied that a vampire is meant to move on to different area every so often and the ability of speed seems to push that idea to never stay in one place too long, as it is very easy to run. It is not just physical movement that can be exceptionally fast. Speech too can be faster than the human ear can make out.
The ability to use superhuman strength is one of the characteristics that set vampires apart. Edward’s physical strength is seen in stark contrast to the fragility of human Bella. A vampire’s diet does not have a massive impact on the levels of strength, in fact hunger or intimidation can increase strength much like a human when in danger. "Human blood does make them stronger than animal blood, but only fractionally. Big game (bears, wildcats, predators) makes them stronger than the "weaker" blood of herd animals." Ultimately, physical strength is always going to come down to the individual vampire, rather than secondary factors like their diet. Strength, of course, isn’t always physical. It is impossible for a vampire to die through physical starvation but what the lack of blood intake does alter is a vampire’s mental state.
As a person is changed into a vampire, their physical appearance is enhanced, their eye color changes, their hearing and eyesight becomes more acute, their heart ceases to beat, and they no longer need to breathe or blink. Natural changes in the human body do not occur any longer, mainly because the venom replaces all of the natural chemicals processes and functions in the body. As the vampires describe themselves they are like stone, frozen exactly like they were when they were transformed. That is the reason why male vampires have sperm but females can't have children. Males require no change whatsoever to produce sperm, but females must physically change to bear children, so only males can have children but only with human females. Other things, such as fingernails and hair, also cease to grow. It is worth noting that, to a human, a vampire’s body is comparable to granite or marble (though to another vampire the skin feels very smooth and soft); this a reflection of how vampires are essentially unchanging, like "living stone." Vampires can be killed, but it is almost impossible to accomplish, as they are nearly indestructible. The only way to kill a vampire for good is to rip apart the body and burn the pieces. Werewolves and shape-shifters are very capable of killing a vampire, as the two are at a slight advantage over them as long as their combat techniques are up to match. Vampires themselves are the most likely to succeed in killing their own species, as they are equal to their target in physique and mentality (at least this is most likely), unless the target has a special ability or "gift."
Of special note is a vampire's body chemistry, as described in Breaking Dawn's FAQ section on Stephenie Meyer's website. Although vampire skin serves the same basic purpose of human skin to protect the body, the transformation process makes their cells hard and reflective, like crystal. As such, a lubricating fluid that is chemically similar to their venom is produced in order to make movement possible for the vampire. A similar fluid also coats their eyes so they can move easily in their sockets (though actual tears cannot be produced because tears are meant to protect human eyes from damage, which is, obviously, unnecessary for a vampire's eyes); in this same pattern, a variety of venom-based fluids exist to perpetuate bodily functions similar to those that existed when the vampire was still human - even many functions that blood serves in humans are carried on in some form in this manner. (It should be noted that these fluids can't transform humans into vampires the way the actual venom can.) One particularly important effect of this is the presence of a fluid related closely enough to human seminal fluids that it can bond with a human ovum, which is how it is possible for human-vampire hybrids such as Renesmee and Nahuel to be born. None of this shit makes any sense whatsoever, but at least it's a lie you can understand. Another important consequence is the fact that the venom-based lubricant (and, therefore, probably the rest of the fluid types as well) is very flammable(, which makes no sense whatsoever), explaining why setting vampires on fire is so effective. It is likely that the necessity of ripping the vampire's body to pieces before incinerating them is to prevent them from putting out the fire themselves before it can do serious damage.
Transformation from human to vampire is described in Twilight as being "...the sharpest memory they have of their human life." A human is bitten, and venom from glands inside the vampire's mouth is injected into the bloodstream. Depending upon "how much venom is in the bloodstream, and how close the venom is until it enters the heart", the transformation could be anywhere from 3-5 days, but it is interesting to note that if directly injected into the heart then it could only take 2 days. During that time, the human will endure indescribable pain as the venom slowly circulates through the blood and eventually reaches the heart. Once the venom is injected, it is described as being "...the beginning of the greatest pain you will ever understand. The venom then has to make its way all through the body. Next through the heart, and it will pump again and again in the heart until it starts meeting itself in the veins. Then it will burn all the veins until the heart stops beating. It moves slower than blood because it’s thicker. Each beat of the heart can only push it so far. The changing/burning process is slow. The venom has to saturate every cell in the body before it ends." Part of the transformation process involves the human gaining more chromosomes, so vampires have 25 pairs of chromosomes.
All vampires are described as having superhuman strength. Their senses are incredibly keen -- they can smell blood and hear heartbeats from miles away. They also are able to run very fast, and running is described as a second nature to vampires. One of their most significant abilities is their immortality, although if the vampire coven remain in one place for too long (like the Volturi) then after a few thousand years they may take on the appearance of fragility, as Bella describes Marcus and Aro's skin to be like "paper", but they are not fragile. They will live forever unless they are dismembered which they could live through, as body parts can still move and reattach themselves but to permanently kill them you then have to burn the pieces.
A small number of vampires gain special talents from when they are changed into their new form. If they had a characteristic or personality that was very dominant in their human life (such as charisma or sensitivity), it would be possible for it to be magnified into a power or talent after their "change". Some talents mentioned are mind reading, second sight, the ability to change others' emotions, cripple people with their mind and distinctive feels for other vampires' gifts.
Deviations from traditional vampire legend
Vampires in the Twilight world are different from most other literary vampires, per se. One fact is that they have very few weaknesses - they are not harmed by holy water, the sun, garlic, or crosses. Vampires in Twilight are not burned by the sun, but rather their skin sparkles like diamonds in sunlight. Additionally, they have a reflection in mirrors, cannot be killed by wooden stakes and will show up in pictures. Vampires in the Twilight series are also incapable of sleeping. It is unknown what happens to a vampire after they die.
Vampires in the Twilight world are said to have only one natural enemy: werewolves.
Vampires also often fight among each other. There have been many cases throughout history where vampires create armies to eradicate other vampires.
The La Push shape-shifters are also meant to protect the Quiletes from vampires, making them enemies of vampires as well.