a band that play emotive hard core music with rawkus vocals and fairly complex melodies. Slower tempos than most hard core music, its considered 'softer' but trust me, its not really. Generally in thes tyle of bands like CTTS or city of catterpiller.
There are also newer emo bands, such as Hawthorne Heights, who play accoustic peices with soft 'whiny' vocals. This is Emotional Core Bands. and the newest stage of 'emo'
Most people think that Dashboard Confessional is an emo band, and it is, but not in the original sense of the word. Bands like 'Dear Diary I seem to be dead' and 'I Would set myself on fire for you' or possibly even 'funeral' diner' are aslo 'emo' but in the old sense of the word. MCR are a band that is much closer to the original sense of 'emo' except they have made it so more people like it.....
a 'darker' version of emo - much more second wave. That is to say, heavyier and more bass. Also known as Love Metal sometimes. No Accoustic guitares whiny lyrics. More screaming, heavier sounding tunes and random sounds (you cant call them notes really). Think Screamo meets metal.
His Infernal Majesty is the closest im gonna get to an example youd know off :D
Most emo "metal" bands have either long dissappeared or are underground bands. Try it, I did and feel in love with it!