(generally)middle-class bored teenagers who are morbidly attracted to concepts of misery, suffering and death and who wear black or dark coloured clothes to reflect their ethos that 'life is so very depressing when you think about it'. They often have pierced lips, dark makeup, and invariably have long hair, mostly straightened and black, covering part of their face, perhaps to aid their introspective tendencies. They try to stand out but ironically have formed a taxonomy of emos (who all look the same.) Male emos are often bisexual, or pertain to be,kissing each other, because it shows the extent of their perceived emotional scope. They listen to special emo music of which the lyrics concern self-hatred, complaints against the shallowness of other people etc. etc. However, there are varying degrees of emo-ness as some peole (semi-emos) like the dark dress sense, but can't be assed with the whole 'cut me now' syndrome, and these are emos a non-emo could probably have a conversation with.
Emo girl: you guys kiss!
*Emo boys kiss*
Emo girl: ok, stop now
*Emo boys continue*
*Emo girls giggle* Emo girls: look at them! What a turn on!