Audi AG is a German automobile manufacturer with headquarters in Ingolstadt, Bavaria, and has been an almost wholly owned (99.7%) subsidiary of the Volkswagen Group since 1964. The company evolved from Auto Union, NSU, Horch and DKW, the former having incorporated the historic Audi company which was founded in 1910.
The Audi emblem is four overlapping rings that represent the Auto Union. The Audi emblem symbolizes Audi amalgamation of Audi with DKW, Horch and Wanderer: the first ring represents Audi, the second represents DKW, third is Horch, and the fourth and last ring Wanderer.
Source:wikipedia.org