Quattro explained

Quattro:

1. "Ur-Quattro" was the name of a model. It was a coupe.

2. Quattro is also the marketing name of all of Audi's AWD technologies. It has two main variants: the TORSEN-based system for longitudinally mounted engine layout and the HALDEX-based system for transversely mounted engine layout.

The S4 I mentioned is of course a sedan model. Its AWD technology is the most sophsticated among sedans.