Buffy the Vampire Slayer - Introduction

The following synopsis lifted off of Wikipedia;

Buffy the Vampire Slayer is an Emmy Award-winning and Golden Globe-nominated American cult television series that aired from March 10, 1997 until May 20, 2003. The series was created in 1997 by writer-director Joss Whedon under his production tag, Mutant Enemy Productions with later co-executive producers being Jane Espenson, David Fury, and Marti Noxon. The series narrative follows Buffy Anne Summers (played by Sarah Michelle Gellar), the latest in a line of young women chosen by fate to battle against vampires, demons, and the forces of darkness as the Slayer. Like previous Slayers, Buffy is aided by a Watcher, who guides and trains her. Unlike her predecessors, Buffy surrounds herself with a circle of loyal friends who become known as the "Scooby Gang."

The series usually reached between four and six million viewers on original airings

Writer Joss Whedon says that "Rhonda the Immortal Waitress was really the first incarnation of [the Buffy concept], just the idea of some woman who seems to be completely insignificant who turns out to be extraordinary." This early, unproduced idea evolved into Buffy, which Whedon developed to invert the Hollywood formula of "the little blonde girl who goes into a dark alley and gets killed in every horror movie." Whedon wanted "to subvert that idea and create someone who was a hero.” He explained: "The very first mission statement of the show was the joy of female power: having it, using it, sharing it."

Main characters
Buffy Anne Summers (played by Sarah Michelle Gellar) is "the Slayer", one in a long line of young women chosen by fate to battle evil forces. This mystic calling endows her with dramatically increased physical strength, as well as endurance, agility, accelerated healing, intuition, and a limited degree of clairvoyance, usually in the form of prophetic dreams.

Buffy receives guidance from her Watcher, Rupert Giles (played by Anthony Stewart Head). Giles, rarely referred to by his first name, is a member of the Watchers' Council, whose job is to train and assist the Slayers. Giles researches the supernatural creatures that Buffy must face, offering insights into their origins and advice on how to kill them.

Buffy is also helped by friends she meets at Sunnydale High: Willow Rosenberg (Alyson Hannigan) and Xander Harris (Nicholas Brendon). Willow is originally a bookish wallflower; she provides a contrast to Buffy's outgoing personality, but shares the social isolation Buffy suffers after becoming a Slayer. As the series progresses, Willow becomes a more assertive character, a powerful witch, and comes out as a lesbian. In contrast, Xander, with no supernatural skills, provides comic relief and a grounded perspective. It is Xander who often provides the heart to the series, and in Season Six becomes the hero in place of Buffy who defeats the "Big Bad". Buffy and Willow are the only characters who appear in all 144 episodes; Xander is missing in only one.

Influence
Buffy's success has led to hundreds of tie-in products, including novels, comics, and video games. The series has received attention in fandom (including fan films), parody, and academia, and has influenced the direction of other television series.

Source.