I'll ask two dif Urban Dictionaries to help me explain:
From AbsolutePunk.net: EMO in MUSIC =
Emo (an abbreviation of "emotionally-driven Hardcore punk") is a term now broadly used to describe almost any form of guitar-driven alternative rock that expresses emotions beyond traditional punk's limited emotional palette of alienation and rage. It is also used to describe fans of this genre, most commonly teenagers. (e.g., emo kid). The actual term "emo" originated in the mid-1980s D.C. scene, with the band Rites of Spring, as well as bands such as Fugazi, Moss Icon, and Antioch Arrow.
From Urbandictionary.com: EMO KID=
COOL EMO KID: doesnt care what ppl think, likes a good band whether they are on mtv or not, and won't stop listening to some band just cuz everyone suddenly 'discovered' them. they do nothing to make ppl feel bad for them, and want no ones sympathy. they give everything a chance before deeming it cool or uncool. and if they want to kill themselves, they do it. they dont shop regularly at hot topic, but dont' completely disregard it. if there's something they want to buy, they go for it, and dont deny they bought it there. most of what they wear is from hand me downs, a garbage, a thrift shop, or was found. they dress how they want, and never deliberately try to piss ppl off or 'rebel'. if they do something rebellious, it is not just to be rebellious, it is because they want to/believe in doing it. they respect people who dont want to put drugs in their body, but some COOL EMO KIDS do drugs because they feel like it.
I'm WAY too old to be considered ANY kind of "kid"...but I AM EMO. That band i pointed you to (My Chemical Romance) is very EMO. If you like that song I highly reccommend "I'm Not OK." I cant post the link here at MS though. It contains some light het and hom sexual content.