M4A and MP3: A Codec Story
M4A stands for "MPEG-4 Audio". It usually contains audio encoded with AAC (Advanced Audio Coding), which was designed to be the successor to MP3. At low bitrates, AAC sounds better than MP3.
However, MP3 (MPEG-1 Audio Layer III) remains the king of compatibility. Every digital device made in the last 25 years can play an MP3. When you convert M4A to MP3, you are trading a small amount of theoretical efficiency for maximum practical utility.
