Emo vs Punx :)  

Emo is another form of Punk. The music differences between the two are that Emo usually deals with depressing topics, and teenager angst, whereas Punk usually sing about rebellion and the counterculture. Both styles of music have the same rhythm structure, tunings, and chord progressions, but differ in content and lyrics.

In short, Emo is a mix of the Goth, Punk, and Grunge subcultures.

Unfortunately, Emo and Punk are starting to become mainstream, and it's very hard to come across an 'actual' Punk or Emo. You can usually tell by their attitude, and how much money they have.