
Podcasting consists of creating sound archives and distributing them by means of a file RSS(is a current format like .mpg or .avi) that it allows to subscribe and to use a program that download it, so the user listens to it at the moment that he wants, generally in a portable reproducer, like a Portable PC.
Also I think Apple/iPod, were the first Software that starts using it.
Credits-->
http://en.wikipedia.org/wiki/Podcasting
http://podcast.com/
http://www.elpais.com/podcast/