Audio Files are file extensions used to play, open or edit sound files (files you can hear such as music). There are three major groups of audio file formats: Uncompressed audio formats, such as WAV,...
WAV is Window's native lossless audio format
.AIFF is Apple's native lossless audio format
.MP3 is a common compressed audio format
.OGG is slightly less common
There are many many more
Download and install an iPod cconverter. Google: free ipod converter. Jodix offers a free converter for iPod. It's the one I use. Very user friendly and it works.