Simply, a genre of Electronic Dance Music based around a non-straightened half-step beat, wherein a bass-drum (kick) will often (but not always) play on the first
downbeat and a
mid-range percussion (snares, claps, etc.) playing on the third downbeat, with variations to this skeleton beat. It is often produced around 140BPM, but can go as low as 128 or even as high as 145, there is no real set BPM.
Sometimes it is said to be a
downtempo genre but this is simply a misunderstanding of the concept of a half-step beat.
LFO modulated low and midrange basslines are not essential to the genre and alot of dubstep productions do not even incorporate them (e.g. Nero - Reaching Out, Bassnectar Remix -
Ellie Goulding - Lights), and actually originated from it's origins in 2-step garage and Dub Reggae, and can be found in DnB and House.
Expanding on this, frequently, alot of songs that aren't Dubstep are referred to as Dubstep, mainly due to incorporating alot of features (LFO-Modded Bass, Dirty FM Synthesis
Mid-Range, etc.) associated with Dubstep.
There is no specific feel to dubstep. It can be
thrashy, heavy and dirty (e.g. Skrillex, Excision, etc.) or melodic, euphoric and trancey (e.g. Seven Lions,
Xilent, etc.), or moody, relaxing and chill (e.g.
Skream, Bassnectar, etc.). It can incorporate elements of a variety of different genres ranging from Trance and DnB to Hip-Hop and Nu-Metal, and the reverse is also true.