What is the difference between trance and progressive trance?

http://techno.org/electronic-music-guide/

Trance is a genre of electronic dance music that developed in the 1990s. It is characterized by a tempo of between 110 and 150 beats per minute, repeating melodic phrases, and a musical form that builds up and down throughout a track. It is a combination of many forms of sound such as techno, house, pop, chill-out, classical music, and film music.

Trance employs aural dynamics to a great degree: a characteristic of virtually all trance songs is the soft mid-song breakdown, beginning with and occurring after the orchestration is broken down and the rhythm tracks fade out rapidly, leaving the melody and/or atmospherics to stand alone for anywhere from seconds to a few minutes. When vocals are present in trance, they are generally sung by a female with a soaring, operatic voice ranging from mezzo-soprano to soprano, best described as "ethereal female leads floating amongst the synths".