Armin van Buuren: Wii loves trance ..... or else

[radioioRobert]

This answer could have many layers, to make it really simple:

http://en.wikipedia.org/wiki/Trance_music
http://www.last.fm/tag/trance

That'll at least give you the basics. My love is progressive house/progressive breaks, but those links are a lot more "big picture".