A Podcache is a Geocache where the cache information is provided in audio form (usually in MP3 format)
Podcaches can talk you thru an environment (be it a park or hiking trail etc..) and will usually require you to note down information along the way to be used to find GZ at the end. They can also be used to provide audio clues, similar to a mystery geocache where you listen rather than read.
A good podcache would require the use of a GPS at some stage in the proceedings to help find the cache.
Geocaching Australia allows podcaches to be listed and you may upload 5 MP3 files of no more than 1MB per file. This should allow approximately 1 minute of standard encoded audio per file but avoid people using Geocaching Australia as a music host.