hahaha (if only we didn't know what it meant)
http://en.wikipedia.org/wiki/Emo_%28music%29
This will explain everything.....
I would read it myself, but all this 'Is it post-hardcore, original emo or screamo?' stuff bores the crap out of me, but this is (if anyone is interested) in typical Wikipedia style the most comprehensive guide to this overused and lazy term.