Human

Humans are the basic stock in the Twilight series, from which vampires, shape-shifters and werewolves originate. Lacking vampiric enhancements, they are considered prey by most vampires, who need their blood for sustenance. Not hunting human beings, the Cullens and the Denali live on a purely "vegetarian" diet, based on animal blood, which is however much less appealing than human blood. In the Twilight movie, Edward states that "Its like a human living on tofu, it keeps you strong, but you're never fully satisfied". In the book Twilight, vampires compare eating human food to eating dirt for human beings.

Human beings who discover the existence of vampires are considered a threat, and a Volturi-enforced law has been implemented dictating that said humans either be killed or changed into vampires, causing Jane, Demetri and Felix to be sent to Forks in both the novel and the movie Eclipse', where they're joined by Alec. It is also illegal for human children to be turned because they are usually dangerous and untrainable, due to their lack of concentration and self-control. The Volturi tried for decades, if not centuries, to train said children, utterly failing. A human to be changed into a vampire needs just to be bitten and enough of the venom to enter their bloodstream. If blood is consumed by the vampire during this time, it is highly unlikely that he will resist the temptation to kill the human before completion of the transformation. The pain accompanying the transformation is described as the worst one possible by all those transformed into vampires, and in Breaking Dawn, it is described as a burning feeling by Bella. A human, however, can also be changed into a werewolf by being bitten by one, and it remains unknown whether the conversion is painless.

Trivia
According to Aro, the human race has now weapons that could kill vampires, but wouldn't have the chance to use them, thanks to their strength and velocity. The situation, however, worries him.