Fanfiction.

Fanfiction refers to fan-written stories about a celebrity, book, TV show, movie, cartoon, anime, comic book, or other form of entertainment. While, as just mentioned, they exist for every type of media, and books are perhaps the most popular form, there is a thriving community of fanfiction for anime, cartoons, and animated movies. These stories can greatly range in quality, in terms of plot, character development, and faithfulness to the original content.

If you are going to start reading fanfiction, you have been warned- there is no way out. You get sucked into the fandom, and never leave. Fanfiction, while not the best at points, is addictive. So, if you do plan to read it, just watch out. Speaking of which, there are some things you might want to know if you are thinking about reading fanfiction. For example, some words and language. This language are also basic fangirling terms that any fangirl needs if they are to join a fandom/become a fangirl. There are other needed words, but these are words that apply specifically to fanfiction, though. They are as follows:

Ship= (as a verb)- to like two characters together: (as a noun) a pairing of two characters as a couple
OTP= One true pair- the one ship you ship above all else
Fluff= When two characters (often a ship) do something that makes you have the feels in an adorable, lovable way. When the characters are being cute and having a cute interaction ex. a character comforts another character when they are sick.
The Feels= overcome by emotion at how cute, tragic, happy, or anything else something is
Lemon= a particularly sexual story- I'd stay away from those if I were you
Songfic= a fanfiction based on a song, that often has the lyrics and a bit of the story that accompanies those lyrics
Oneshot= Any one-chapter fanfiction. These vary greatly in length.
Drabbles= a collection of oneshots in chapter form

Just a general note- if you see some weird name that isn't the name of one of the characters, its a ship name. Break apart the name, and you will get parts of two of the other characters' names. Those are the two that make up the ship.
Ex. Hiccstrid (How to Train Your Dragon) = Hiccup + Astrid

A link to the fanfiction website:
https://www.fanfiction.net/