Podcasting is the distribution of audio or
video files, such as radio programs or music videos, over the
internet using either RSS or Atom syndication for listening on
mobile devices and personal computers. A podcast is a web feed of
audio or video files placed on the Internet for anyone to subscribe
to, and also the content of that feed. Podcasters' websites also
may offer direct download of their files, but the subscription feed
of automatically delivered new content is what distinguishes a
podcast from a simple download or real-time streaming (see
below).
Podcasting's essence is about creating content (audio or video) for
an audience that wants to listen when they want, where they want,
and how they want.
for more info, pls refer to wiki