An M4A file is an audio file saved in the MPEG-4 container format. It may be compressed with either the Apple Lossless Encoder (ALE) or Advanced Audio Coding (AAC). The M4A format support 16 and 24 bit, multi channel audio, as well as ID tagging.
Important: AAC compression is lossy, meaning some quality is lost in the compressed file. The Apple Lossless Audio Codec (ALAC) provides lossless compression, which means no quality is lost in the file compression process.