Trance is indisputably one of the most emotional genres that actually exists, because it is all self-interpretation. There are no instrumental or musical limits to trance, and rather than listening to some random guy screaming about his life, associating with a trance progression or hookline is much more deep, and much more personal.
Like other genres, trance has many subgenres, some of which have become very commercialised to the extent where the musical merit of some tracks must be questioned (eg. Flip'n'Fill, Scooter etc.)
At the higher end of the more uplifting, melodic (and relatively popular) styles of trance are DJs such as Tiesto, Armin van Buuren, and Ferry Corsten. These DJs in particular can make beautifully structured mixes their own music, and the music of others, building it into a euphoric collage which spans multiple energy levels, in order to provide the listener with peak/trough feelings, and carry them through numerous emotions and mental states.
The creation and spread of trance music is mainly down to machinery such as the Roland JP-8000 (providing the prominently manipulated supersaw wave), and experimental DJs such as Sasha & John Digweed.
Trance has a strong influence from early Detroit techno, but tends to be more dramatic or "emotional" than the minimalism of earlier techno. Common elements in trance include heavy, compressed kick drums, dramatic sweeping pads, and cascading synth arpeggios.
As with any kind of music, there are a billion sub-classifications possible -- hard trance, psytrance, acid trance, goa trance, etc. Trance has been one of the most popular forms of club music over the past few years, and has arguably produced more mainstream appeal (Oakenfold, Van Dyk, etc.) than most other electronic sub-genres.