Age / Sex / Location. The mating call of the barely post-pubescant teenager. Typically the male initiates this signal, as an attempt to attract a female that can give an honest reply to his liking. More often, however, the male is fooled by another male, generally much older, who will impersonate his "dream girl" for his own sick, sadistic pleasure.
Horny teenager: "A/S/L?"
50yr old bald, obese guy sitting naked at computer, scratching double chin and eating cheetos: "16/F/hopefully in your bedroom soon ;) "
Horny Teenager: "Wanna cyber?!?!"
50yr old dude: "Thought you'd never ask!!!!!"