A lot of times, when we talk about horror, what we're really talking about depends a lot on the medium we're discussing. Like if I say horror movie, you're* probably thinking of an 80s slasher flick or something in that genre. But if I say a horror book, you'll probably think of Stephen King. Which is interesting, right? Because almost all Stephen King books you can think of are also movies.
* A generic you, not you specifically.