Downtempo (or Downbeat) is a laid-back electronic music style similar to ambient music, but usually with a beat or groove unlike the beatless forms of Ambient music. The beat is sometimes made from loops that have a hypnotic feeling. Sometimes the beats are more complicated and more featured instead of being in the background, but even then they are usually less intense than other kinds of electronic music like Trance.
Often the name chill out music is used to refer to songs demonstrative of the genre, but those names also refer to other styles of music, and downtempo encompasses a wider variety of styles than those terms alone would indicate.
Another related genre is Trip hop, though Downtempo usually uses a slower tempo than Trip-hop. Due to the relaxing and often sensual or romantic feel of most downtempo music, along with the absence or minimal use of lyrics or vocals, it is a popular form of background music in 'chill out rooms' of dance parties, many alternative cafes, and is often marketed as being good music for lovemaking.