I've always thought that it was a cultural thing - that it's the same instrument, but a violin is the name for it in classical music, and a fiddle for - for instance - Irish jigs.
It's the same instrument, but generally the fiddle is held differently. A fiddler holds the instrument at the shoulder or chest, with the fiddle neck held lower than you see Andre playing above..
Thanks for the input (and the young chap on the video). I can't say that I fully understand the technicalities of how each instrument is played but I at least know that it is actually the same instrument played in different was.
I must admit to enjoying Andre Rieu - but mostly in the non-classical music.
Brenden - I think that I read that somewhere, no matter the heritage of a musical instrument I would be incapable of making any noise that could be considered to be even a small bit musical.
Andre seems to take orchestra music to the masses - I even saw a clip of him playing violin with a 3 year old violinist.