A history and definition of dubstep:
Dubstep is a form of electronic dance music that evolved as an offshoot of UK Garage in the early 2000s. Dubstep typically between 135-145 beats per minute in tempo, includes heavy use of sub-bass frequencies and commonly features a “halfstep” drum pattern with a kick on the first beat of the bar and a snare on the 3rd beat of the bar.
It is worth noting that although the tempo and halfstep drum pattern are common features of Dubstep, these are not hard and fast rules and it is very common for Dubstep producers to experiment with different tempos and drum patterns such as the 2step rhythms commonly found in UK Garage.
The only universally agreed upon “rule” is the heavy use of sub-bass. The sound spawned in South London, namely Croydon, where the seminal Big Apple record shop, as well as other key record shops, had their origins. It was here that many now key DJs had their early influences and would trade beats which was not quite house, not quite garage. At 140 beats a minute originally, it differed from the 4x4 beat music that was in vogue at the time, and whilst still an unknown quantity in around 2004, it was slowly getting a cult underground following due to the internet and the easy way of sharing “dub plates” via instant messaging and so forth.