What is the difference between a Lure (Luuuure) and a Fly ?

What is the difference between a Lure (Luuuure) and a Fly ?
Somehow I stumbled upon this video and this guy just managed to piss a bunch of people off.  In the process a discussion ensued regarding exactly what the difference is between a Lure and a Fly ?


According to the commenters: An artificial fly must have Some natural materials, if not, it`s an artificial LURE!!!


Because

#1, The steel in the hook is artificial, doesn't occur in nature, man MAKES it from iron and carbon!

#2 In fact ALL FLIES are classified as lures by the IRS for Federal Excise Tax purposes,

#3 As well as the US Commerce Department for Import Duties!

Tying a Czech Style Nymph by Davie McPhail

This method originated in the Czech Republic where it was used to great effect in the International Fly Fishing Championships. Since then it has been widely adopted by fly fishing enthusiast around the world.

In principle the method is not new – as it presents the right flies at the right depth in a natural manner in a way in which the takes can be easily spotted. In principle the method is simple, short-line deep-water nymphing that covers all of the water.