Gender Combinations:
M - Male
F - Female
m - Younger (teens) Male
f - Younger (teens) Female
b - Boy (under 15)
g - Girl (under 15)
S/s - Shemale (boobs, penis, balls, no vagina)
H/h - Hermaphrodite (boobs, penis, vagina, usually no balls)
Mdom - Male dominant
Fdom - Female dominant
A slash between them indicates the combination: i.e. M/F means "male/female" or Fdom/m means "female dominating younger male." Heck, it doesn't even need to have a slash necessarily (MFffs might mean "male/female/two younger females/shemale"). A plus sign indicates "plenty" (mF+ would mean "younger male/plenty of adult females"). Parenthesis with two letters separated by a | indicates that the character can or will transform between two genders, i.e. (M|g) indicates "a man who can and/or will transform into a little girl", or (F|H) indicates a "woman who can/will transform into a hermaphrodite."
Stuff that happens:
BND - Bondage
F/O - Forced-Orgasm
MC - Mind-Control
NC - Non-Consensual
TRN - Training (to become a slave, etc)
Milk - Lactation (breastmilk)
MILF - Mother I'd Like To Fuck
Xfrm - Transformation (from one creature to another, usually)
Tor - Torture (ouchies)
Bukkake - Somebody gets COVERED in cum!
SM - Sadomasochism (whips and chains and stuff)
CD - Crossdressing (someone dresses up as the opposite gender)
PWP - "Porn Without a Plot", or "Plot? What Plot?" (naughty stuff happens without necessarily having the essential components of, strictly speaking, a "plot")
nosex - Guess.
unusual skin - Something idiosyncratic to me, but there must be SOME people out there who like it besides me. Green skin, blue skin, charcoal grey, tattooed or striped; even being fuzzy counts under here, depending on the pattern and color (and fuzz). Latex counts, to a degree. It ... turns me on to a disproportionate degree. :3
Types of People
Succu - Succubus (demon which has sex with men in their sleep. That's how the story goes, anyway ...)
Incu - Incubus (male equivalent of succubus)
TG - Transgender (character gets some sort of sex change)
DG - Dickgirl (girl/woman with both a penis and a vagina)
Twin - Two people who are nearly visibly identical. I will generally make it clear, however, whether this is incest or masturbation. ;)