From Hydrogenaudio Knowledgebase

This is the official FAQ from the MPEG Audio Subgroup, maintained by Heiko Purnhagen. It deals with all aspects of this successor to MPEG-1, not only with the ones concerning AAC, but the emphasis is of course on the audio part of this standard.

My advice would be to print it out for further reference and easier reading (7 pages), just like the FAQ about MPEG-4 (15 pages) and the general MPEG Audio FAQ for an overview (4 pages).