Buffy Summers (born circa 1980) is an American vampire hunter, "chosen" by mystical forces to receive the powers and legacy of the Slayer. Her adventures have been chronicled by writer Joss Whedon, first in the motion picture Buffy the Vampire Slayer, then a television series of the same name and currently a comic book as well as several novels by various authors.
The Slayer is a line of young women, typically in their early teens, who acquire increased speed, strength, healing as well as mild prophetic ability (coupled with some more vaguely defined abilities) upon the death of the previous Slayer. Each Slayer is a chosen defender of humanity against demons (which seem to be part of the Cthulhu Mythos). Until recently, there has evidently been only one Slayer at any given time. When Buffy Summers was killed by an elder vampire called The Master (who bore some resemblence to Orlock), but then resussitated medically, another Slayer was "called" resulting in there being two. Circa 2003 a powerful witch named Willow Rosenberg used a magical weapon known as The Scythe (made specifically for the Slayers but lost for centuries) to "activate" all the potential Slayers in the world.
The television series chronicled Buffy's meeting with, temporary enthrallment to, then defeat of a vampire identifying himself as Dracula. According to Charles Loridans (below) this was in fact one of Dracula's "soul clones," a failure who proved unable to control known as Lestat. In a later article on the (now sadly defunct) MONSTAAH website, he also posited that Buffy is a descendant of the Van Helsing family through her father (whose parents were killed by in a car accident, believed to be murder, so that Hank Summers was raised apart from his sister Jaime Sommers, aka The Bionic Woman--all descended from Maria Van Helsing's daughter Helena Summers nee Porter).
Like Doc Savage and other adventurers, Buffy was assisted in her exploits by several close friends and associates, including the aforementioned Willow Rosenberg, Xander Harris, Watcher Rupert Giles and the en-souled vampire Angel.