If you stop someone on the street and ask him or her for a list of movie genres, they’ll probably recite a few familiar ones: action/adventure, comedies, dramas, documentaries, and so on. If you ask a few folks, you’ll probably hear lots of overlap between them. I’d also venture most people’s lists have less than ten items in them.
Netflix’s list of genres, on the other hand, has tens of thousands of items in it. Of course, nobody is expected to navigate such a long taxonomy by themselves; instead, the system uses it to recommend new movies to its users. Somebody who’s looking at an “absurd stoner comedy” (an actual Netflix micro-genre) may be interested in more, so the system recommends others grouped under that genre.
This 2014 article on The Atlantic on how these “micro-genres” work is a must-read for information architects. And if you want explore them yourself — and possibility discover a weird new movie — here’s a complete list of Netflix’s micro-genres.