There is a 1979 song made popular by British band The Buggles called “Video Killed the Radio Star.” It spoke of the advent of modern technology, specifically video, and its effects on radio. One repeated line goes “We can't rewind we've gone too far,” but just like fashion, radio stars have resurfaced in a new digital form: podcasters.
For those of you that still remember, one of the major features of radio broadcasting was the radio shows, which are like the soap operas of today. They were on a regular schedule and episodic, basically the definition of podcasts. Podcasts are usually audio files, although you may occasionally get video (vodcast), or a PDF file.