Everyone reads it. Nobody admits it.
Fanlore defines slash as: "a type of fanwork in which two (or more) characters of the same sex or gender are placed in a sexual or romantic situation with each other." The term most likely comes from the virgule, or forward slash, because writers would tag their works like "Kirk/Spock" or "Harry/Draco".
Slash is a category of fanwork.
I'll explain the history, different permutations, the reasons behind creating it, and talk a little bit about public opinion.
[Warning: I will not be posting any explicit images, but in my discussion of the subject I will be alluding to mature subjects. Be wary when searching for more information on the subject. And feel free to comment or message me if you'd like to know more!]
Derivative fanworks and slash have existed for centuries.
Yeah, I'm for real. By derivative fanworks, I mean anything that uses the characters and/or setting from another story. 'Wicked' by Gregory McGuire fits this example. So does the Biblical art hanging in museums around the world. The concept of intellectual property is a fairly new one; people 'borrowed' characters and ideas from other creators all the time.
Okay, but slash?
Yup. Obviously, fandom and derivative fanworks have changed a lot since Plato wrote his 'Symposium', but careful readers will note that he not only shipped Achilles and Patroclus, he had very particular feelings about how they expressed their love for one another.
"The true love of Achilles towards his lover Patroclus— his lover and not his love (the notion that Patroclus was the beloved one is a foolish error into which Aeschylus has fallen, for Achilles was surely the fairer of the two, fairer also than all the other heroes; and, as Homer informs us, he was still beardless, and younger far)."
The relationship Homer portrayed in The Iliad was a platonic one. Plato did not feel this was the case. Greek culture had changed a lot since Homer had written The Iliad, and homoeroticism had become the norm, so it makes sense that writers would re-imagine the heroic characters of their culture so that they fit in with contemporary ideas. Of course, not everyone was in agreement. Plato was writing in response to a lost play by Aeschylus, who felt that Achilles played a very dominant role in the relationship. Plato felt that the opposite was true.
Fandom as we know it today evolved around Star Trek in the late 60s and early 70s.
And with it came slash. Fans were enamored of the show and the idea that it presented a better future than the one we have now. They were so exuberant they began creating fanworks in homage to the characters and stories, disseminating them in fan zines and at conventions (remember: this was before the internet was a Thing).
These fanworks are where slash as we know it today evolved. The majority of slash fanworks featured a male/male pairing. Often, these relationships were depicted as sexual (if they were platonic relationships, fans used an ampersand to indicate this). At the time, homophobia was extremely prevalent among the fan community, as was misogyny. Since then (as now), most slashers were women, their behavior was discouraged and their contributions to the fandom were minimized.
As Trek fans attached themselves to new fandoms (Doctor Who, Star Wars, and The Sentinel), the terminology they had developed carried over and became integrated in fan culture.
It hasn't been welcomed with open arms.
The Harry Potter and Supernatural fandoms have gone through periods of unrest over the prevalence of slash in their communities. Sometimes fans are wary of creating spaces with explicit fanworks, because it would be easily accessible for minors. And while it's not a requirement, a lot of slash is definitely explicit. While plenty of minors actively seek out that kind of content, it is the responsibility of adults to take precautions and make sure they're not sharing that kind of content with someone underage.
Other fans created their own archives and chatrooms that centered around specific pairings, or banned any slash that wasn't about a heterosexual pairing. It's not like homophobia is over. And slash fanworks still primarily feature a homosexual pairing. Which means that even in fan communities, slashers have not always been welcomed.
Fans with differing opinions on the subject have tried to find ways to coexist. During the 80s and 90s, fans began to categorize their own fanworks to make them easier to find (or ignore) by giving a rating to their content. Fans have used the MPAA system, as well as one of their own devising. It's called the Citrus Scale.
Citrus- the most mild interactions on the scale, such as a romantic hug or a kiss on the cheek. Orange-used for kissing, hugs, and some more touching beyond that that begins to have a hint of sexuality. Lime- goes further into the sexual, with heavy making out and possibly some light groping. Some might not have these, but rather qualify as a lime for hinting at lemon-scale action. Lemon- has explicit sexual content. Grapefruit- is generally said to be the X-rated or truly bizarre lemons.
This was also the era of "don't like don't read", which essentially invited fans not to participate if they stumbled upon something they didn't enjoy.
Because of all the backlash (both public and private) that slashers received, anonymity was extremely important. The emphasis on fan spaces as 'private' (for fans only) has carried over through today. This is because outsiders often don't understand what's going on. They leave unhelpful comments on stories and artwork (if you're not the target audience, you're probably not going to appreciate a piece). And frequently they ask why we waste so much time focusing on well... two dudes kissing. Among other things.
So why bother?
This is a difficult question to answer, because every fan is going to have a different answer. Many in the Trek fandom expressed a desire to see their favorite characters addressing taboos that the television show was not able to address due to network censorship. At the time, their works were very transgressive, and were often created in response to social movements and the AIDS crisis.
Other fans cite a lack of content tailored to their interests. The majority of slashers are women, and while most mainstream media is saturated by the male gaze, female viewers are often alienated by a lot of the sexual content being produced. So instead of settling for media that makes them uncomfortable, they create their own. This in a way follows in the transgressive tradition of early Trek slashers.
Slash has grown to become more that what it was. It is still transgressive, but the culture that has evolved around the creation and consumption of slash is a major part of the experience.
The state of fandom now reflects the state of the internet: (almost) anything goes. The same is true of slash. After Fanfiction.net deleted a lot of explicit slash fics en masse (primarily targeting stories with homosexual content), fans created Archive of Our Own (Ao3), a site run by the Organization for Transformative Fanworks. The Archive makes tagging easy, and encourages fans to self-filter content.
User toastystats (decisiontoast) analyzed the content on Ao3 and reported that most of the fanworks hosted by the site are m/m slash. The second image on this block is a breakdown of their research.
Femslash, or slash pairings with two women, is less popular than gen (no pairing) and heterosexual slash pairings.
The reason for this is extremely complex. Part of the problem is the lack of female characters. There simply aren't as many female characters to pair together. Of course, some writers cisswap or genderswap their stories, which means that they take two characters who were originally presented as one gender, and create a fanwork where those characters are a different gender.
Other fans argue that part of the problem is internalized misogyny in the fan community. Because slash communities evolved around m/m ships, there is a large part of fandom that assumes m/m is the default. Fans are working to correct this bias in the community, as well as discouraging fanworks that bash female characters.
Fans are having similar discussions about characters of color, and working to make fandom a more inclusive space.
Real-person slash (or RPS) often faces the same backlash as other slash, with some extra baggage. Because these fanworks are about real people, there's an element of discomfort that a lot of fans have about the medium. It's certainly understandable: With fictional characters, there's no risk that the star of your explicit story or art will end up seeing it. With real people, it's not just a risk. It's something that actually happens.
Though in the clip Daniel Radcliffe isn't reading RPS (he's reading slash about the character he played), incidents like this make fans very uncomfortable. Fanworks have been dismissed and mocked by talk show hosts and showrunners. Fans don't appreciate their work being laughed at, or taken out of context so that it loses all meaning.
Fans also don't *intend* to make celebrities uncomfortable.
Of course there are exceptions, and celebrity culture definitely encourages personalities that disrespect the boundaries of famous people by treating them as commodities. Overall though, RPS is written for the fan community, and is not intended to be consumed outside of that community.
Slash is not exclusively an English-speaking experience. Trek fans helped to shape the personality of modern fandom, but their growing pains have been replicated around the world. This suggests that slash is not an aberration, but is in fact a natural part of fandom. Some fans in China, for example, have been legally penalized by their government for writing slash fic. The K-pop community is currently grappling with the fact that many fans are underage. There are also concerns that music studios encourage their stars to sexualize themselves, but discourage homoerotic slashing, which seems to be punishing fans for taking their experience to the next logical step.
Still with me?
The slash community has spent a long time growing into what it is today. Slashing has become a specific kind of fan experience, and while it's not universal and the opinions of the group are far from monolithic, the experience itself is sort of a rite of passage among fan communities. First and foremost it should be fun, without impeding on anyone else's ability to have fun. From there, well, everything goes, right? ;)