A brief history of Yaoi in anime and manga, incase you were curious.
Yaoi is manga and or anime produced by women for women. It focuses on relationships, both romantic and otherwise of men together.
Yaoi is not the same as gay porn. It is what is attractive to women, not gay men. Yaoi is a genre that shows the common female fantasy that m/m relationships are highly romantic, angsty, loving, and above all, extremely sexy.
The men in Yaoi anime and or manga are exteremely beautiful. You might even say more beautiful than humanly possible. The relationships in the Yaoi genre are extremely romantic, and the ones involved in them are often heroes of some sort or another.
Yaoi works are sometimes very explicit, and are definitely not for kids. However, even though some of them are very explicit, the anatomical aspects are generally not shown, for the reason of aestheticism. Much of the time, a strategically placed limb, or blurring is used to cover what would normally be in the southern region of the body.
Yaoi originated in Japan. A country that has a long history of admiring male beauty. Yaoi began with Japanese soldiers who had forged close bonds with each other. About thirty years ago though, was when the first Yaoi was really published. Soon after came a branch of Yaoi called 'Shounen Ai' or Boys Love. This genre features mainly younger members who have relationships that are complex and angsty. (Like Shuichi and Yuki.)
Boys love sparked a huge trend for girls, who began to put their favorite characters into yaoi and shounen ai situations. Yaoi grew popular, and that's when they actually started calling it Yaoi. Yaoi translated basically means: 'no peak, no point, no meaning.' It can also be taken as 'All in fun'
Yaoi first came to America in the early 90's. Whether it is shounen ai, yaoi, professional, ametuer or otherwise, it is still called Yaoi.
I don't know what else to write o.O If you have anymore info that you'd like to add, please let me know. Much of this information came from Yaoicon.com. You should really go check it out if you're a fan of the genre. The con is great!