Ambient

Ambient music is a musical genre that focuses largely on the timbral characteristics of sounds, often organized or performed to evoke an "atmospheric", "visual" or "unobtrusive" quality. Ambient evolved from the early 20th century music of the impressionists, composers such as John Cage, Morton Feldman and minimalist composers and early electronic composers of the 1960s and 1970s, to rock musician Brian Eno, who is responsible for coining the phrase ambient music in the manifesto liner notes of his 1979 album Ambient 1: Music for Airports.

Ambient music has influenced many other genres, most remarkably some forms of rhythmic music presented in chill-out rooms at raves and other dance events, with the intention of creating a calmer, relaxed atmosphere for ravers to take a break from dancing.

Source : http://en.wikipedia.org/wiki/Ambient_music