Think of it as a way to right a wrong, or a way to continue something that ended way too soon.
Its taking a book, film, TV show, play, etc. and making it what you and hopefully other fans want. Don’t like the way it ended, rewrite it. Don’t understand why the writers can’t see that two characters NEED to be a couple? Write them together. That movie should have a sequel or be a trilogy! Then write them.
Shows that have been cancelled way too soon have had 2 or 3 more seasons due to fanfic writers keeping it going. In some cases these virtual seasons as they are called are considered cannon.
Some are written for contests where you’re given criteria, some are written based on prompts someone gives you and others are just born out of the writer’s minds.
There are hundreds of thousands of fan fics out there. Supernatural alone as over 120,000. Its acknowledged and even read by people associated with the show. The actress who played Shadow on Arrow read a couple of mine. Talk about nervous!
If you read any you’ll notice there are rules that we writers have to follow. Ratings for what the target audience is, if there any triggers such as kidnapping or anything else that could trigger someone reading it to have painful memories resurface or a PTSD event.
It really is a great way to get something you’ve written out there and writing a wrong is always enjoyable.
If you have any questions or comments just ask.