According to Wikipedia - a podcast is an episodic series of spoken word digital audio files that a user can download to a personal device for easy listening. Well that's one way of putting it but the effectiveness of podcasts come as they recreate the connection that radio has with the listener. It's a much more friendly medium, particularly for interviews where the way a question is answered is as important as the words that are spoken. That's can't be said to television or video where body language is also important as there is generally too much at stake to get anything like an honest answer from the interviewee.