to have accepted canon in a show or book or real life changed to siut facts that are currently convienient to the author.

Name comes from Buffy/Angel fanficiton due to the fact that the shows' creator Joss Whedon constantly did this, causing considerable irritation to fans and fanficcers worldwide.

To understand this term it's good to know what the individual words mean in the context that they are in.

Yaoi is the Japanese word for male homosexuality. Put simply it means "gay". The word is actually an acronym that comes from the Japanese phrase, "YAma nashi, Ochi nashi, Imi nashi." meaning no climax, no point, no meaning. Yaoi has also come to describe a particular genre of Japanese shows (anime) and comics (manga) that depict male homosexual relationships. These types of shows are becoming increasingly popular among (mostly) female fans of anime and manga. Fans of yaoi often take their favorite male characters, from any anime or manga, and pair them together (regardless of sexual orientation in the original story).

The second word, lemon, is a term used amongst the fanifiction community. Quite frankly it means that there will be a graphic sex scene in any story designated as a lemon. These types of stories would be ratedp either NC-17 or X by the MPAA. Usually authors will inform the reader of any lemons at the beginning of a story. Lemons refer to any type of sexual activity that includes penetration of some sort. Another term that is used alongside lemon is "lime". This is simply a less graphic description of sexual acts. These stories usually do not go further than heavy petting. Lime's are also more commonly referred to as "shonen-ai" meaning boy's love in Japanese.

So if we combine the two words the meaning is: a story that graphically describes the se...

A word used to say how angry you are, made popular by the fanfiction FaCe ThE StRaNge

Stories written around or composed entirely of original characters (OCs). Tends to be a better form of fanfiction than that made up of nothing but canon characters, as it's a lot harder to mess up those characters' personalities. It's highly recommended that anyone trying to get into fanfiction should start out doing OC fiction.
Games such as Warhammer 40,000 and Dungeons and Dragons almost demand that you write OC fiction for them, since there are very few canon characters (none but the gods in D&D, and they can act pretty much how the writer wants them to within a certain boundary). As such, these make excellent starting areas for authors looking to get into OC fiction.
If you're writing OC fiction, make sure that every character you add to the story is taken through the Mary Sue Litmus Test first, unless you want to get flamed. Mary Sues have killed many a good piece of fanfiction with their sickening, unrealistic perfection.
OC fiction often allows readers to submit their own OCs; don't just accept them out of the kindness of your heart. If they're Mary Sues, or don't fit within your story, ...