What, apart from a God-awful racket? :-) Actually dubstep is electronic dance music that's defined by the rhythm. It has evolved from" drum and bass" which in turn evolved from "Jungle", and started out in the underground music/party scene which is pretty big in England. It is very dark sounding with a very heavy bass line that is typical of it's genre and separates it from house music, or techno which has a steady even repetitive beat all the way through.
In recent years, dubstep has found it's way into mainstream music, but is a softened down version that is probably more acceptable to people who enjoy chart music. Generally it's enjoyed by the younger generation!
The only time I personally have enjoyed dubstep is at Glastonbury Festival, with a band called Sam and the Womp! They create their music using real instruments eg a trumpet, saxaphone and keyboard, and the dubstep "womp" is created by a tuba! It doesn't do them justice but here is a link to a song they've put on youtube.They are very light hearted and the vid is good fun. (My son would direct you to much more serious dubstep artists but he's not the one answering this question!). If you ever find yourself at a large(ish) festival in England, also check out "The Correspondents" and you will find yourself in the position of dancing uncontrollably to "grown up" dubstep! :-)