** Spoiler Alert!!! click to hide or show**
Basically, a vampire is a being who has an energy deficiancy, or is unable to keep their own life energy level high enough to sustain them. Therefore, these people must take energy from others to keep themselves healthy. No one truely knows exactly how vampires came to be, or where the vampire myths were spawned.
** Spoiler Alert!!! click to hide or show**
There are three types of vampires I know of:
Sanguinarians: The blood-drinking vampires.
Psi-vampires: Those who feed from the life energy of others, mostly without the 'donor' noticing much other than feeling tired.
Sexual vampires: Incubus for males and Succubus for females, these are vampires that feed off of the energy released during sex. 
