Emo = Emotive Hardcore. Hardcore punk played in minor chords and a heavy focus on introverted lyrics. Started in the mid 80s by bands like Rites of Spring and Fugazi.
Urgh, emo, bad bad music for people who like self-indulgent pity. At least be angry at the world like the goths or the neds.
The Get-up Kids Mineral Bright Eyes Cursive At the Drive-In Hot Water Music Jimmy Eat Worl The Anniversary Sunny Day Real Estate Reggie and the Full Effect Rainer Maria The Get-up Kids A New Found Glory Braid Dashboard Confessional American Football Promise Ring Atom and His Package Alkaline Trio Sparta Thursday Piebald The Juliana Theory Taking Back Sunday Coheed and Cambria Rilo Kiley Further Seems Forever Texas is the Reason Straylight Run Death Cab for Cutie Brand New Jawbreaker Mars Volta Rites of Spring The Starting Line Something Corporate Desaparecidos Minor Threat Fugazi Saves the Day (Just a few examples)
Now I wouldn't consider any of those bands as 'hardcore' - more like modern (American?) emo punk tbh. I know "Emo" is supposed to be short for emotive hardcore but I feel it has started to more describe bands such as listed above which, in my opinion, are just 'emotional punk'. As quad said, emo-core is how I would describe stuff like Underoath, A Static Lullaby, The Prisoners Dilemma, Before Today etc. Stuff that's a bit screamy and riffy but still comes with emo whines, lyrics and breakdowns. But that begs the question, where does screamo come in? K? I love this Genre Wars game.