Trance as a electronic dance music was developed in the 1990s. It is charcterized by a rate of 130-160 bpm, repeating melodic synthesizer phrases and a sound form that builds up and down throughout a record. It was made as a mixture of largely Techno and House. It is called "Trance" because of its morphing repetitious beats and throbbing sounds, which can put us into the state of trance. Now it is very popular music played almost in every nightclubs and discos. It is not a easy-listening music, it has complicated construction and a big number of played in one moment samples.
Trance have also many sub-styles, I try to list some of them:

- Acid Trance
Early 90s style with characteristic bass-line made with the help of Roland TB-303.

- Anthem Trance
Also called Uplifting Trance because of  progression in all elements like lead synth, bass and treble chords.

 - Classic Trance
Originated in early 90s is original form of this music, with less percussion than techno and more melody.

 - Euro-Trance
It is very commercial style of Trance made as a mixture of hard trance and Eurodance.

 - Goa Trance
Very interesting kind of Trance originated in early 90s, special form of sound named for Goa, it is often uses the Raga.

 - Hard Trance
Agrgresive and fast sounds, it was born in !993 in Frankfurt.

 - Psychedelic Trance
It was developed in mid 90s, better known as Psytrance. It is related with Goa but less melodic and more abstract.

 - Chill Trance
Also known as Ambient Trance, it was influenced by chillout downtemp style of  relax music. Can be very melodic and mellow, some pieces contain also ethnic features.