About horror subgenres:

Anthologies
Wikipedia
These are films that contain more than one story, which may be interconnected, or completely independent of each other.

Asian horror
Mostly this will be Japanese horror (or J-horror), but I may include some horror from other Asian countries, like Korea, et al. To be honest, though, I've generally only heard of any Asian horror movies because of American remakes, which I'd probably like better than the originals. Still... I do have some desire to check out the originals, and maybe even some Asian movies that haven't been remade here. We'll see.

Classic horror
These are mostly Universal Monster Movies from like the 1910s to 1950s, though they don't all have to have been made by Universal, nor do they all have to be monster movies. Really, it's just any horror films that were made in the 1950s or earlier.

Comedy horror
TV Tropes; Wikipedia
These movies are intended to be both funny and scary, though the ratio between the two may vary from film to film.

Family horror
This subgenre includes both animated and live-action films. Many of these films barely qualify as "horror," if at all. But some of them may be scarier than your typical kiddie fare. And, of course, "family" doesn't mean "just for kids"; some of the movies here could be enjoyed by people of any age. (I may also include some movies that are primarily meant for kids in other subgenres instead of this one, if I feel like they're possibly a little too scary for kids.)

Folk horror
TV Tropes; Wikipedia
I guess it's a subgenre of "religious horror," which mainly involves pagan faiths, superstitions, cults, and such, though it can sometimes include more modern, mainstream religions. It may or may not involve supernatural elements. It's most likely to be set in rural, isolated communities. It may take place in the distant past or the present, or anytime in between. It probably has elements of psychological horror, and possibly other horror subgenres. I'm not sure there's any sort of consensus on what movies can be considered folk horror; for the most part I'll rely on the judgment of various websites, but I may disagree with some things being called folk horror, as well as judging some things to be folk horror myself, even if other sites don't categorize them as such.

Gothic horror
TV Tropes; Wikipedia
It may be hard for me to say exactly what's meant by this subgenre. I tend to think of it as sort of Victorian, which means most such movies will be set in the 1800s, usually in England. But they can really be set in any time or place, as long as they have a sort of Victorian feel about them. And it's even harder for me to say what I mean by that, though it could involve very old mansions (if set in modern times), which might have been built in the Victorian era. (Or not.) Anyway, there should just be a certain sensibility to these films, a sense of macabre elegance, or what have you. I dunno.

Holiday horror
Wikipedia
The term technically applies to horror movies set on or around Christmas. But I'm going to include horror movies that are specifically set on or around any holiday (provided the holiday plays an important part in the story). However, it excludes Halloween movies, which have their own section in my film reviews.

Monster movies
Wikipedia
I originally included these films in my horror section, but have since moved them to their own sections, the main one being "monster movies". That can include classic movies as well as modern ones. They can be about things like mummies, werewolves, and other miscellaneous creatures. vampires and zombies have their own sections, as do giant monsters (such as Godzilla). However, I will include any movies here that are about multiple kinds of monsters. For things like witches and ghosts, see "supernatural horror".

Psychological horror
TV Tropes; Wikipedia
This can include movies that might fit in other subgenres, like "supernatural," or "monster movies," or "thrillers," etc., and indeed it may be difficult for me to decide whether to file some movies in this category or one of those (particularly with psychological thrillers). But the important thing, to me, is that the psychological fear characters in the films endure is more central to the film than anything external. (Which is not to say there won't be external things that very much warrant fear.) In some cases, though, the fear (either that of characters or viewers) may be largely derived from characters having psychological issues that actually alter their perception of reality, and potentially make them dangerous. (However, they generally won't realize this about themselves, and probably won't be overtly homicidal, as would characters in other categories such as "slashers" or "thrillers.") But there will also be some movies I list here where the psychological aspect is more a direct result of some external threat, but... I differentiate it from "thrillers" because it's just more... horrific. I guess. (Or because it's as much about screwing with the minds of characters and/or viewers as it is about putting the characters in danger.)

Religious horror
TV Tropes; Wikipedia
This may or may not involve supernatural elements, but it often does have things like demons or possession. Sometimes it's just cults who may believe in supernatural things that don't actually happen in the film. It can overlap with Folk horror, or be more modern. In any event, it has soemthing to do with religion, whether Christianity (particularly Catholocism), or anything else.

Sci-fi horror
TV Tropes; Wikipedia
It seems pretty straightforward to say that some sci-fi movies have horror elements. Although I may not always agree with some people (or with Wikipedia) whether any given movie necessarily fits either label, sci-fi or horror. So... we'll see.

Short films
This is for any kind of horror film that is less than 40 minutes long.

Slasher films
TV Tropes; Wikipedia
So, this is basically about perfectly normal psycho killers. No monsters or supernatural stuff (usually), though such things can sometimes intersect with slasher films. There are subgenres of slasher films in which I have no interest, like "splatter films", though some slasher films I do watch may include a fair bit of gore. Or not.

Supernatural horror
Wikipedia
This, as I said before, is for things like witches and ghosts. Or demons. Or people with supernatural powers. Or really, just any horror with any kind of supernatural elements. It may intersect with other subgenres of horror, like Folk, etc.

Thrillers
These are in their own section, as they're not quite horror movies, but they can certainly be scary, so I might as well mention them here. They often involve psychological elements. They may or may not involve killers, though when they do, the killers (usually) aren't necessarily psychotic. And I guess I don't know what else to say.