A teenager, or young person who only ever listens to mainstream music, that is usually in the top 40.
As soon as they hear of a band that is not mainstream, they label it as 'an unknown band', and refuse to listen to it.
These people cannot appreciate the art of music, and see it just as something to dance to and talk about with their other little top 40 friends.
The kind of people who only knew who Good Charlotte were, after they sold themselves out and released those pop songs that were massive for a while.
Top 40 kid: "Has everyone heard the new Akon song? It's the best song I've ever heard!!"
Other Top 40 kid: "Nah, i was too busy listening to Miley Cyrus and Britney Spears, OMG, and Lady Gaga"