M4A is an audio file created in the MPEG-4 format which is a multimedia container format used to store compressed audio and video data. M4A files are similar to .MP4 video files since both file types use the MPEG-4 container format, but M4A files only contain audio data. It contains audio encoded with either the Advanced Audio Coding (AAC) codec which is a lossy compression. Both M4A and MP3 file extensions are used for audio-only files, audio-only MPEG 4 container files generally have an M4A file extension. M4A files are unprotected, while the protected files have an M4P file extension. The use of the .m4a extension ascended due to the misunderstanding between MPEG-4 video files and MPEG-4 audio-only files. The iTunes Store delivers songs in the M4A format. These songs are encoded using AAC compression, which significantly reduces the size of each file. M4A file quality is better and file sizes smaller compared to MP3 files. Important: Mac Media Player 11 requires the K-Lite Codec Pack in to play M4A files. However, Mac Media Player 12 provides intuitive support for the M4A files format.