As you'd expect for a company with thousands of films in its archives, Netflix meticulously catalogs every film in its library. Unlike us peons, though, who are happy enough dividing films by their genre or how much nudity they contain, Netflix takes everything into account when it adds a new film or TV show to its library.
Netflix's proprietary algorithm sorts films based on everything from historical settings to whether or not it contains vampires, allowing them to cater to almost ludicrously specific tastes. As an example of how laser-like the focus of Netflix's genre algorithm is, for an April Fool's joke they once suggested users check out "Movies Featuring an Epic Nic Cage Meltdown." Which may as well have just been a list of every Nic Cage film, but you get the idea.
In 2014, a curious statistician worked through the code of Netflix and found the site has over 75,000 different "micro-genres" that it uses to categorize movies and shows (76,897 to be more precise). These genres are largely hidden from the user, and most people will barely see even a fraction of them while browsing, which is kind of the point. It's your Netflix account. So if you're not interested in period movies featuring sexy werewolves, it's not going to suggest them to you. But then, who's not interested in sexy werewolves?