iTunes was one of the biggest boons to getting podcasts accepted. Podcasts are episodic audio productions that people listen to whenever they want. How does their podcast listening software know when there's a new episode? You guessed it, via RSS feed. When you submit a podcast to Apple, you tell them the url of your RSS feed so your listeners can find new episodes. It's RSS 2.0, with a few additional fields. OK, a LOT of additional fields for things like: category, image, duration, keywords, subtitle, and summary. The industry was then left scratching its collective head asking "so what's the difference between description and summary?" Nobody quite knows. The bottom line is, if you're going to be playing in Apple's sandbox, you got to play by Apple's rules. If you're going to submit a podcast to iTunes your RSS feed should have these extra elements.

The iTunes RSS description