Background on Buffy

Buffy the Vampire Slayer is about a lot of things. There is the first and most blatant metaphor, which is that high school is a hellish place, full of personal demons and the monsters other people become. However, there are more subtle elements, about the pitfalls of growing up, and the trouble we get into as we age, and our hormones change, and we begin to pull away from parents and grade-school friends. For instance, Buffy herself loses her virginity on her 17th birthday, to the only vampire to have a soul (forbidden love), but his afterglow causes him to lose his soul. In the show, a soul is a metaphor for a conscience, a sense of morality, and without it, he is literally a different person, cruel and violent, which echoes a common complaint of hundreds and thousands of young women- "He was a completely different person after we slept together". Buffy's best friend, Willow, is dating a boy who becomes a werewolf, another metaphor for the wild teen years.
After the high school years, the issues become a little more blatant, but still handled slightly obliquely. When Willow's boyfriend decides he can no longer control his wild instincts (a female werewolf is a trigger in this- potential infidelity as a breakup cause), she begins to explore a wider world. In the process she joins a different religion than her parents' (she was raised Jewish but embraces Wicca, the same path I followed) and falls in love with a woman. Willow cautiously and nervously comes out of the closet to Buffy, and Buffy's first reaction is shock- she calls Willow "Will", as if that will make it easier to think of her as in love with a woman. However, once she recovers she is very happy for her friend, and soon there are on-screen kisses and cuddles, and even a scene in which Willow and her girlfriend perform a spell which is clearly a metaphor for sexual contact, with heavy breathing and arched backs, though only the palms of their hands touch.
Buffy's main focus is the vampires and demons she fights, but she also has to deal with real-world issues. Some of these issues are layered with metaphor, like the Mayor, whose motivation is to become a Demon and devour the town. This is the literalizing of the idea of the corrupt politician, who just wants more power and doesn't care who he hurts on the way. Some are stark and harsh, like Buffy's mother's illness. She is diagnosed with a brain tumor, is operated on, and comes home with a clean bill of health. She is just beginning to recover and resume her normal life when she has an aneurysm and dies. Buffy is the one who finds her at the beginning of the episode, and the rest of the episode focuses on the terrible practicalities of autopsy, funeral arrangements, and survivor's guilt. It is an episode without music of any sort, so we are focused on the words people say, and, more importantly, the silences. There are many awkward silences, and moments of uncomfortability. There are also awkward conversations. One such involves a character who was a demon and has recently become human. Her mission as a demon was to inflict pain and death on humans, but she rarely stayed, and never thought of them as people. However, she has become friends with Buffy's mother, and, like a small child, she wants to know why it has to happen, why this vital, loving woman has to cease. She is struggling with something we all have to wrestle with at some point, the loss of innocence, the understanding of death as part of life in this world. Willow's girlfriend, on the other hand, lost her own mother during high school, and so she has wise words, and can comfort Buffy to some extent, reassure her that her expressions of grief may well take odd turns, and that's ok.
All of this is a guide for us the viewers. We come to know and love these characters, to cheer for their struggles and mourn their losses, to grow and explore the world with them. We relive the awkwardness of first love, or, for younger viewers, get some idea of what to expect and what to avoid. We empathize with the drive to move out from under our parents' roof, the stress of finding a job that can support you, the wonderful-scary feeling of finding the person you want to spend the rest of your life with. The show is a fun-house mirror, our own worries and hopes distorted, writ large, but still recognizable as human impulses. This is the strength of Buffy, and why it is truly literature, and not just pop culture.