It's an electronic wind instrument. I use it primarly on all my VSL mixes (still mixing one to show off).
It's basically another way to input MIDI other than a MIDI keyboard controller. It has touch sensitive pads, and a breath sensor, as well as pitch control.
I use it on all single line instruments (strings, winds, brass, etc)
It makes the expressive quality of VSL even better imo, but takes getting use to play each type of instrument realistically. Since I am primarily a wind player, it also improves my writing and ideas a great deal.