What is the difference between M4A and AAC Audio Files?

Question

is there a difference between M4A audio files and AAC audio files or are they exactly the same thing but with a different file extension ?

Answer 1

.M4A files typically contain audio only and are formatted as MPEG-4 Part 14 files (.MP4 container).

.AAC is not a container format and instead it is a raw MPEG-4 Part 3 bitstream with audio stream encoded.

Note that M4A does not have to contain exactly AAC audio, there are other valid options as well.