Oh gawd you views are newbish...
Here in simple terms:
Emo- Wears black all the time, has fringe over large percentage of face, often cuts/harms self, has eye shadow and black fingernails, talk about how life sucks, gets dumped by girlfriend, listens to songs about people killing themselves.
Punk- Often have some form of un-natural colour in their hair (red, green, blue etc.) which is spiked in some way. A lot of punks have Cuffs (those black things with studs) around their wrists, or an anarchy symbol. Wears mostly black. Has a black belt with studs.
Goth- Harder to describe :P. Black hair, black eye shadow, black nails, black lips, pale skin, wears black, often believes in paganism/witchism or some form of nature worship. A percentage of Goths are satanists and worship the devil and preform sacrifices and the like.
Finally, the following bands are not Emo.
Green Day and Good Charlotte