In its original incarnation, the term emo was used to describe the music of the mid-1980s DC scene and its associated bands. In later years, the term emocore, short for "emotional hardcore", was also used to describe the DC scene and some of the regional scenes that spawned from it. The term emo was derived from the fact that, on occasion, members of a band would become spontaneously and literally emotional during performances. The most recognizable names of the period included Rites of Spring, Embrace, One Last Wish, Beefeater, Gray Matter, Fire Party and slightly later, Moss Icon. The first wave of emo began to fade after the breakups of most of the involved bands in the early 1990s.
Starting in the mid-1990s, the term emo began to reflect the indie scene that followed the influences of Fugazi, which itself was an offshoot of the first wave of emo. Bands including Sunny Day Real Estate and Texas Is the Reason put forth a more indie rock brand of emo, which was more melodic and less chaotic in nature than its predecessor. The so-called "indie emo" scene survived until the end of the 1990s, as many of the bands either disbanded or shifted their style to the mainstream.
As the remaining indie emo bands entered the mainstream, newer bands began to emulate the more mainstream style, creating a style of music that has now earned the moniker emo within popular culture. Whereas, even in the past, the term emo was used to identify a wide variety of bands, the breadth of bands listed under today's emo is even more vast, leaving the term "emo" as more of a loose identifier than as a specific genre of music.
http://en.wikipedia.org/wiki/Emo_(music)
I didn't read it,just a definition of "Emo"