WAV, AIFF, MP3 and MIDI files	(a very brief introduction)	William Wieland
WAV files (Windows) and AIFF files (Macs) are uncompressed audio files. They are the files you usually edit. They are relatively large.
MP3 files are compressed audio files. They are smaller and therefore easier to share and store. AAC is a similar format used by iTunes. OGG and M4A are two more types. Compressed audio files are called lossy because some data is lost in compression.
MIDI files are simply instructions for a sound card or synthesizer to play. MIDI files are the smallest of all.