I found some nice short definitions of BL, Yaoi and Shōnen’ai in this article...
I had to go to Wikipedia for the Bara related explanations, so it's more influenced by the Japanese history and development of the genre and is longer.Article by Emma Hanashiro (2015) “What is BL/Yaoi [Definition, Meaning]
First, it is important to note that the definitions of Boys Love, yaoi, and shōnen’ai outside of Japan are different than their meanings within Japan. In countries outside of Japan, the following is a breakdown of the meaning of these terms:
Boys Love (often shortened to BL):
A relatively new term used to indicate broadly manga, anime, or fan works depicting love between men for a presumed female audience. These relationships between men are often sexual and have determined and visually codified “top” and “bottom” positions. The “top,” also called the seme, “attacks” or rather gives love to the “bottom,” or in other words the uke. Throughout this article, I will mainly use Boys Love as an all-inclusive term for media depicting male/male couplings.
While yaoi is used like Boys Love to describe a genre with works focused on men loving men for a female audience, it has the additional connotation of depicting graphic sexual scenes. In typical advanced search options for anime and manga online, yaoi appears far more often than Boys Love, and is used in conjunction with shōnen’ai.
When used in opposition to yaoi, shōnen’ai means a boy/boy manga or anime without any explicit sexual scenes. It is often viewed as focusing more on story rather than hot and heavy action between two men.
In Japan, however, there are slightly different meanings to these words. This has much to due with the history of the Boys Love industry and the gradual development of the genre over the past forty years.
So what's you're opinion? How do these genres/subgenres apply to the west today? If you're a developer what are you trying to incorporate. If you're a player or reader what are you hoping to see and/or expecting to see?Bara
Although sometimes conflated with yaoi by Western commentators, gay men's manga or gei comi, also called Men's Love (ML) in English and bara in Japan, caters to a gay male audience rather than a female one and tends to be produced primarily by gay and bisexual male artists (such as Gengoroh Tagame) and serialized in gay men's magazines. Bara is an even smaller niche genre in Japan than yaoi manga. Considered a subgenre of seijin (men's erotica) for gay males, bara more closely resembles comics for men (seinen) rather than comics written for female readers (shōjo/josei). Few titles have been licensed or scanlated for English-language markets.
Yaoi has been criticized for stereotypical and homophobic portrayals of its characters, and for failing to address gay issues. Homophobia, when it is presented as an issue at all, is often used as a plot device to "heighten the drama", or to show the purity of the leads’ love. Matt Thorn has suggested that as yaoi is a romance narrative, strong political themes may be a "turn off" to the readers. Critics state that the genre challenges heteronormativity via the "odd" bishōnen ("beautiful boys"), and Andrew Grossman has written that the Japanese are more comfortable with writing about LGBT themes in a manga setting, in which gender is often blurred, even in "straight" manga.
Bara is more true to actual gay male relationships, and not the heteronormative relationships between the masculine seme and feminine uke types that are the most common romantic fantasy in women's yaoi manga. In comparison to yaoi, gay men's manga is unlikely to contain scenes of "uncontrollable weeping or long introspective pauses", and more likely to show characters who are "hairy, very muscular, or have a few excess pounds". Compared to gay men's manga, yaoi is "more careful to build up a strong sense of character" before sex scenes occur. The men in bara comics are more likely to be stereotypically masculine in behaviour and are illustrated as "hairy, very muscular, or [having] a few excess pounds" akin to beefcakes or bears in gay culture. While bara usually features gay romanticism and adult content, sometimes of a violent or exploitative nature, it often explores real-world or autobiographical themes and acknowledges the taboo nature of homosexuality in Japan.
The gachi muchi ("muscley-chubby") subgenre of boys' love, also termed bara among English-speaking fans, represents a crossover between bara and yaoi, with considerable overlap of writers, artists and art styles. This emergent boys' love subgenre, while still marketed primarily to women, depicts more masculine body types and is more likely to be written by gay male authors and artists; it is also thought to attract a large crossover gay male audience. Prior to the development of gachi muchi, the greatest overlap between yaoi and bara authors was in BDSM-themed publications such as Zettai Reido, a yaoi anthology magazine which had a number of openly male contributors. Several female yaoi authors who have done BDSM-themed yaoi have been recruited to contribute stories to BDSM-themed bara anthologies or special issues.