Emo is often confused with Emotional Sensitivity, and is more often linked to boys then girls, because of the so very 'unmanly' manner in which an emo boy acts.
Male emotional senstivity is a guy who does not feel the urge to be a macho pea-brained asshole whos only emotion is arrogance and violent anger. A sensitive male realizes that guys can cry, and say the word 'beautiful'. They can also like flowers and admit that there are other guys out there that are hot, and do lots of other 'gay' things while completely content with their heterosexuality.
(an interesting thing about this is that it is quite ok for girls to sit on each other's lap and hug and go to the washroom together etc etc and not be considered homosexual, but if a guy strikes up a random conversation on the bus with another guy, he's a faggot
This being said, an EMO (short for emotional) is someone (guy or girl) who has taken the dark, evil, brooding, shadowy and mysterious genre that goes by the name of goth, and mutilated it into a subculture of whiney sniveling teenagers. An emo is someone who dresses very similar to a goth, wearing makeup and black clothes, but is easily defined often by the lopsided swooping haircut that causes them to be half blind all the time.
A goth makes you uncomfortable standing next to them on a long bus ride, and if done right are dark and creepy and cool looking. Take the band Type O Negative, for example.
View Pic: (urbandic seems to add random spaces so check before pasting into browser and remove any you see)
Emos most of the time have a look of eternal sorrow pasted on their face, and spend their time whining because life is so tragically devestating and heartwrenching. They cry and snivel and cut themselves to gain attention, as opposed to the noble masochistic origin of the hobby. When you see an emo you will want to puke because of how synthetically pretty and childish they look, and then drop kick them.
Emos have ruined the very normal practice that is talking about emotionally hard times to someone close.
"How are you today?"
'Well, to be honest, I feel really lonely. I sit at home more than I'd like and don't really have
(m)any friends. *shrugs apathetically*'
"zOMG... Don't be so emo..."
'...You asked how I was. I am telling you honestly how I am feeling.'
"EMO. Cry me a river... *emo tear*"
This video will familiarize you instantly to what an emo is, if you are still confused in any way: (again, remove any spaces)
I'm gonna kick the shit out of those whiney emo faggots.