Although vampires are the primary supernatural species in Buffy the Vampire Slayer, the number of known witches expanded rapidly as the canon grew, featuring a handful of significant witches, numerous covens, and several other minor witches that might be difficult to keep track of. Buffy the Vampire Slayer introduced witchcraft early on in the series, but it didn't become a prominent feature until Willow dove into the world of magic headfirst, gaining power as she went on. Willow began using small spells in season 2, but she quickly found herself addicted to magic, using it to solve all of her problems (and frequently causing new ones in the process).

https://screenrant.com/buffy-vampire-slayer-every-witch-canon-show-comics/