M4A - MPEG-4 Audio File is a common file type that is used to save audio and video files. These types of files are also similar to .MP4 files since they use the same type of formatting. M4A files include audio data only, and that happens to be the biggest difference between the two. If you own an iPad, you should already be familiar with this type of format. That is because you can purchase this file format from the iTunes store. Different audio can be played using different formats. There are songs that have a copyright protection that have a .M4P file. Lastly, if you want to use Windows Media Player 11 to play M4A files, you will need to make sure that you have a K-Lite Codec Pack. That is the only way that it will play these files types. This is yet another very popular audio file besides MP3.