It's based on a comic book series that started in 2014.
The character Sabrina Spellman first appeared in Archie's Madhouse #22 in October of 1962, and soon became one of Archie Comics' most popular characters. She received her own volume in 1971 and an animated show, Sabrina the Teenage Witch, to go with it.
In her early incarnations, Sabrina was a bright and bubbly "good witch" who fit seamlessly into the gee-gotcha Archie universe. But in 2014, writer Roberto Aguirre-Sacasa re-imagined the character and her story for the rebooted comic series Chilling Adventures of Sabrina after the success he had with Afterlife With Archie -- a serialized horror-spun take on the classic Archie characters. Aguirre-Sacasa's Sabrina retained her innocent facade, but the world around her was far more hellish. Instead of hand-waving easy magic, the Chilling Adventures Spellmans are Devil-worshippers pledged to the Dark Lord who worship at the Church of Night. The mythology is darker, deeper, and macabre -- a true horror story.
Aguirre-Sacasa transitioned from comics to TV and launched the hit CW series Riverdale in 2017. Though he originally planned to bring Sabrina onto that show, he later decided to keep Riverdale more firmly planted in reality (i.e. no magical witches), and thus Chilling Adventures of Sabrina was developed as a TV series for Netflix. The Netflix show looks to hew to the plot of the comics' first volume, in which Sabrina has to make a choice between witch life and mortal existence with her boyfriend, Harvey Kinkle.
One major difference between the comics and Chilling Adventures, however, is that the comics are set in the 1960s, whereas the show is set in contemporary America. Don't let the suspicious lack of cellphone use fool you!