2WD v. AWD

[Mark Trank <mtrank%acva@mail.co.albemarle.va.us>]

Can anyone give me a quick and definitive response to the following:  a 
local mechanic recently opined to me that the quattro system operates (in 
normal mode) in front-wheel drive; only when activated (i.e., 
differential activated) does the four wheel drive mode kick in.  I 
understand differently --that quattro is AWD at all times but that you 
have the ability to direct more power/traction to the front or rear 
wheels when activating the front/rear differential.

TIA,
mtrank@acva