What is WAV?
WAV (or WAVE), short for Waveform audio format, is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs. Though a WAV file can hold compressed audio (alaw, ulaw, ima adpcm, creative adpcm, microsoft adpcm, mp3 codec etc), the most common WAV format contains uncompressed audio in the linear pulse code modulation (LPCM) format. The standard audio file format for CDs, for example, is LPCM-encoded, containing two channels of 44,100 samples per second, 16 bits per sample.

What is M4A?
M4A stands for MPEG-4 Audio, and it is a popular audio file format. Most people are familiar with MP3 and how it shrinks down the file size of songs and other audio files. M4A does the same thing as MP3 does, but even better. Quality is better and file sizes are usually smaller than MP3 files.

What is the difference between M4A and MP4 files?
The existance of 2 different file extensions that can be used to represent MPEG 4 Audio files is unfortunate. MP4 files may or may not contain MPEG 4 Audio. If you see a M4A file you always know that it contains only MPEG 4 Audio. MP4 can be used for MPEG 4 video files, combined video and audio files, or just plain MPEG 4 audio. It is recommended that you use the .m4a file extension rather than .mp4 on your audio files.