The genre that most of the world refers to as Dubstep is an aggressive spin off of the more laid back type of Dubstep that rose to prominence in the UK in the early 00's. It is sometimes derogatorily referred to as "Brostep" by Dubstep purists, due to the stereotype of the crowd that frequents events that cater to this type of Dubstep.
Dubstep typically resides at 140bpm, and tracks typically tend to revolve around the "drop", often after large buildups.
The sounds used are often very distorted, and typically tend to have a focus on harsh mid-range sounds. A large bassline also helps to add to the drive of the track. In the early days of the genre, the basslines were usually oscillated, creating the "wub" sound that has become a stereotype of the genre. In addition to this, there are hooks that provide melodic and rhythmic content to the track.
By this stage, the popularity of Dubstep has slowly diminished over time in favour of other newer genres, primarily Trap and Glitch Hop. In some instances, tracks shift between genres multiple times during the duration of the track. An example of this is in SKisM - Experts.
This is when Dubstep was most popular worldwide. Many of the people getting into EDM for the first time had never heard anything as intense and aggressive as Dubstep, and it was suitable music for festivals and clubs, so there is no surprise that it took off to the degree that it did.
Many Dubstep producers did not just stick to one genre, preferring to diversify and dabble in an abundance of bass-heavy genres such as Drumstep and Moombahton. It was not uncommon for EPs from Dubstep producers to contain a multitude of genres on a single release.
Though Borgore seems to enjoy taking credit for ruining Dubstep, most would agree that Skrillex is perhaps the largest influence in the popularisation of the Dubstep genre. He created a fairly unique and "accessible" style of dubstep that caught on with American audiences, which helped propel Dubstep to popularity worldwide.
Around this time is when Dubstep became an arms race between producers to see who could created the "filthiest drop".
A number of the current most popular Dubstep producers established themselves around this time. Many of them hailed from the UK, where the original Dubstep genre was first birthed.