96 A6 Quattro Drive Belt

[S P SHERMAN]

I am looking for a definition of Drive belt on these cars.
 
I am starting to look for a replacement to my old 86 Avant 5000CS quattro, and am checking into a an A6 Quattro. The current owner is not a mechanic, and his mechanic mentioned that this car needed a "drive belt" replacement (for about $400). He said it was not a timing belt. Not being familiar with these newer Audis, I can't guess from the description and price what they are talking about.  Can someone enlighten me.
 
Thanks