File with an .AAC extension contains audio data compressed with an advanced method. It is similar to the MP3 files, but it usually contains sound in a better quality, due to more efficient compression algorithms. More often than the ACC extension, for such files the M4A extension is used.

The compression method used in the AAC files contains a lot of improvements in comparison with the MP3 compression. Coding is more efficient for transitional and stationary signals, it supports the frequencies above 16 kHz more efficiently. The algorithm contains a simpler filters bank and the final sound quality is very close to the original.