The M4A (MPEG-4 Audio) format is a container format for audio files that is often associated with Apple's iTunes and other Apple devices. M4A files can use various audio codecs, including AAC (Advanced Audio Codec), ALAC (Apple Lossless Audio Codec), and others. Known for its efficient compression and high audio quality, M4A is a popular choice for storing music and audio files, providing a good compromise between file size and sound fidelity. It is widely compatible with Apple devices and is also supported by many other media players and devices.