Here's some handy terminology for fiction you may find on this page:
Shounen Ai—Literal translation: 'boy's love.' As it says, shounen ai is used to denote stories that focus on the emotions and love between two boys. The act of sex doesn't have to occur at all.
Shoujo Ai—Literal translation: 'girl's love.' As it says, shoujo ai is used to denote stories that focus on the emotions and love between two girls. The act of sex doesn't have to occur at all.
Yaoi—The word 'yaoi' (pronounced pretty much how it looks) is an acronym for 'yama nashi, ochi nashi, imi nashi'; which means roughly: no climax, no meaning, no clarity. Kind of makes it sound like a PWP, huh? In general, the yaoi genre tends to focus on sexual themes and not so much on the relationship or emotional aspects that shounen ai does. Yaoi has come to mean something (fiction or artwork) depicting a male/male relationship.
Yuri—The word 'yuri' (pronounce 'you-rhi') is an acronym for… Well, I don't actually know what this particular acronym is for, but it's used to denote stories similar to yaoi, except that it has to do with a female/female relationship.
June—Pronounced 'ju-neh,' this is the correct term to use for a serious m/m story, be it professional or amateur. It usually refers to original character creations. Long-standing m/m stories with a solid base (i.e. a plot line) are considered june.
Lime—One of those nifty little terms that fic readers should know. It usually denotes something a little heavier than just holding hands, but doesn't give a full blown, explicit sex scene.
Lemon—Yet another term every fic reader should know. It's a nice way of saying that the story in question has lots of graphic sex. Most PWPs tend to be lemons, but I have read a few ::read; two:: that weren't.
PWP—An interesting acronym that is defined in the world of internet fanfiction as story whose only purpose for existence is a sex scene. As I stated in the previous sentence, it isn't always this way, but in most cases it is. PWP stands for 'Plot? What plot?'
Angst—A word derived from German meaning that a story is basically dark and dreary. Very little to no sweetness and light in these fics. They usually involve character torture, be it physical, emotional, or verbal, and occasionally end in death.
Shotakon—In a vague and extremely general sense, stories that are shotakon in nature revolve around the relationship between a grown man and a prepubescent boy.
Rorikon—Like shotakon, but involving young girls. 'Rori' comes from Lolita, thus it is a 'Lolita' complex.