Deep house is a style of house music. It is loosely defined by the following characteristics that distinguish it from most other forms of house music:

* relatively slow tempo (110–128 bpm);

* de-emphasized percussion, including:

* simple yet syncopated drum machine programming;

* gentle transitions and fewer "build-ups";

* less "thumpy" bass drum sound;

* less pronounced hi-hats on the off-beat;

* sustained augmented/diminished key chords or other tonal elements that span multiple bars;

* increased use of reverb, delay, and filter effects;

* frequently, the use of vocals.

Deep house music is often synonymous with lounge music and popular compilations such as Bargrooves, Hotel Costes, Deep Concentration, Café del Mar and Lost On Arrival have blurred the two genres with influences of ambient or electro-downtempo music.

Source : http://en.wikipedia.org