What brand does the term "Audi" refer to?

The term "Audi" specifically refers to the Audi brand, which is known for producing luxury vehicles and is part of the Volkswagen Group. Audi is distinguished for its advanced engineering, high-quality interiors, and innovative technology. The brand's vehicles often feature the signature Quattro all-wheel drive system and are well-regarded in the automotive market for both their performance and design.

The other brands listed—Acura, Buick, and BMW—are separate automobile manufacturers. Acura is Honda's luxury vehicle division, Buick is a brand under General Motors known for its mid-range vehicles, and BMW is recognized as a leading luxury vehicle maker from Germany. Each brand has its own unique identity, product line, and market positioning, contributing to the clarity that "Audi" exclusively signifies its own marque.