Humdinger Folksinger (gee, can I call you something for short? HDFS???)- anyhow, a WAV file is one of many ways of saving a sound file on a computer. It records the sound quite well, but it does make a pretty big file that takes a fair time to transmit over the Internet. That's while you'll see sound files like RealAudio or Shockwave on the Internet - the files aren't as big, so they can be transmitted quicker. A MIDI file, on the other hand, is not actually a sound recording. It's a set of instructions that tell the MIDI synthesizer on your sound card how to play a tune, kind of like a player piano roll. Make sense?
-Joe offer-