Fanfic is pretty similar but also really fundamentally different from original fiction. It’s similar in that you’re writing about things using words, but the way you write about them is completely different because you’re using characters and a world that has already been established; you have to make your fanfic fit into that world, or be a plausible offshoot, or you should just write original fic. With original fiction, you’re starting with a blank page in every sense of the word, even though you can obviously draw inspiration and ideas and information from the world around you. And you’re also writing to a completely different audience; generally speaking, people who like the already created world and who want to read more.
"Oh, can I watch?" she said. And Dympna, who never got her hands dirty, could nevertheless name every cylinder and valve that was lying on the floor, and let Maddie have a go painting the new fabric (over the fuselage she'd kicked in) with a mess of plastic goo called "dope" which smelled like pickled onions. After an hour had gone by and Maddie was still there asking what all the parts of the plane were for and what they were called, the mechanics gave her a wire brush and let her help.
Maddie said she always felt very safe, after that, flying in Dympna's Puss Moth, because she had helped to put its engine back together herself.
Code Name Verity, Elizabeth Wein
Writing starts with reading. We learn by example, by reading something and thinking, hey, I could do that - this is why a lot of new writers end up writing really derivative stuff at first; they're trying to imitate something great they read. Some new writers go straight to fanfiction, which is why there's a lot of wish-fulfillment-y self-insert fanfiction out there to go along with all the wish-fulfillment-y self-insert original fiction. Early efforts at fanfiction are often pretty simple too. This is the kind of stuff that goes viral to be mocked around the internet - an authorial self-insert goes to Hogwarts and ends up with everyone falling in love with her, etc. Simple=/= bad, by the way - I think this kind of fanfic can be great fun and well-written, and even if it's not what I personally want to read, someone had a lot of fun writing it, which is good - but that's a topic for another time. At some point, the new writer starts having more and new ideas of their own, and the rest is history.
Anyway, most fanfiction goes a bit deeper than the stereotypical Mary Sue fic and starts deconstructing the canon world. Modern day alternate universes, even, the "what if the characters of Harry Potter were teenages who worked in a coffee shop" type stories are doing this - they ask things like: what character traits are intrinsic? What are a result of circumstances? How would things be different or the same with these characters in different circumstances? These are the questions that I think most fanfiction attempts to answer, whether or not the particular fic does it well. Essentially, it's literary analysis but way more fun. By writing fanfiction, you can take apart a story, a world, a character, and put them back together. Maybe even put them back together better! This helps with writing in a few ways. First, you learn why authors decide to write things in the way they do, and second, you learn why you write things in the way you do. You learn from where you disagree with the authors, where you think the writing is weak, what you would do differently.
You can learn all this from original fiction too, but I myself think that if you're going to learn how to build something, first you should learn to take apart a functional model and see how it works. As much as I hate the training wheels type metaphors for fanfiction, I do think that in this way it can be like a sandbox; you get to mess around at will and get better at writing while writing stories about Hermione being awesome.
Fan fiction is a way of the culture repairing the damage done in a system where contemporary myths are owned by corporations instead of by the folk.Just kidding, that's not actually what he said, it's a misattribution. Anyway, someone said it, and I completely agree. There's a view of stories, books, etc., these days - that they belong to someone who owns the rights, to Disney, to the writer themselves. Legally, that's entirely true, and also plagiarism is bad. But on another level it's just completely off base of the point of telling stories. Stories change, get retold, misinterpreted, and are rewritten all the time. As they should be; a story is a living thing, like language. And as with language, the only unchanging stories are dead ones.
One tends to think of it as written by total fanboys and fangirls as a kind of worshipful act, but a lot of times you’ll read these stories and it’ll be like ‘What if Star Trek had an openly gay character on the bridge?’ And of course the point is that they don’t, and they wouldn’t, because they don’t have the balls, or they are beholden to their advertisers, or whatever. There’s a powerful critique, almost punk-like anger, being expressed there—which I find fascinating and interesting and cool.”
It's not all about my new age-y feelings on what a story means; fanfiction is also a way of challenging the dominant culture, a culture that prioritizes the narratives of white, cisgender, heterosexual men above all others. Is fandom activism? No. But it can overlap with activism. It can challenge assumptions and start a dialogue. And a lot of people get very upset about people writing straight characters in gay relationships, imagining characters as a different race than their canon one, writing about if a cisgender character were actually trans. There's a feeling of "get your icky hands off my characters" about this kind of distress, like those of us who belong to marginalized groups should just be happy with what we get. And fanfiction challenges that. And it challenges the "image" of characters like, for example, Captain Kirk as a straight man. Fanfiction asks: what if this man, who is brave, and strong, and smart, and a cultural icon, was actually gay? What if gay characters didn't just get assigned to the role of sassy friends, villains, and women who get killed before their time? And what if straight men could identify with and admire a gay character without the world ending?
Fanfiction is fulfilling a fundamental need that people have: to see themselves in media, as whole people, and maybe even with a happy ending or two.
No writing is wasted. Did you know that sourdough from San Francisco is leavened partly by a bacteria called lactobacillus sanfrancisensis? It is native to the soil there, and does not do well elsewhere. But any kitchen can become an ecosystem. If you bake a lot, your kitchen will become a happy home to wild yeasts, and all your bread will taste better. Even a failed loaf is not wasted. Likewise, cheese makers wash the dairy floor with whey. Tomato gardeners compost with rotten tomatoes. No writing is wasted: the words you can't put in your book can wash the floor, live in the soil, lurk around in the air. They will make the next words better.
Ending on a happier note than my eternal rage about every lesbian character ever getting brutally killed off, writing is good! Writing more can only help you get better, so keep doing it. And maybe check out fandom, if you have the time. You might find something you like.