This is to let people know of the original meaning of emo. There are so many people on here and on other websites as well as in real person who think they're either emo, or think they know what it means because they've heard it through the mainstream or from their friends.
What emo actually is.
Emotive hardcore, in short, is punk with emotional lyrics (instead of rebellion). The characteristics of emo were fast guitar riffs, like hardcore punk has and shouting vocals but with emotional lyrics.
It all started with a Minor Threat fan named Guy Picciotto who had an idea, for which he then formed a band called Rites of Spring. A fan of the band called Ian Mackaye, who recorded their first album and was a roadie for them, became inspired by this and formed Embrace, who are said to be the second emo band.
The two later went on to form Fugazi who are not firstly recongnised as an emo band, but a post-hardcore band instead.
In the 90s, a second wave of emo hit Washington D.C but this time it was more melodic and softer. More "Emo" if that makes sense. Bands in this wave included Sunny Day Real Estate, Texas is the Reason and many more.
Eventually, in 2001, emo broke the mainstream with Jimmy Eat World's song called "The Middle". From then, emo was played on the radio/TV with bands like Dashboard Confessional and Hawthorne Heights.
From then on, bands like My Chemical Romance, Paramore, Fall Out Boy, Panic! at the Disco have all been named emo and put in to that category. Emo has generally turned in to a teenage phase where it means "emotional" and where it uses darkness to emphasise the wearers emotional state. Many of them are/have self harmed in the past meaning negative stereotypes are created and passed around.