When we talk about "subscription" to a podcast, we mean that the listener will add the podcast to his jukebox application. There are a lot of them, (http://www.podcastingnews.com/topics/Podcast_Software.html).
All of them will use RSS (not HTML) protocol to connect to our site and find out whether any new episodes have been posted. This saves listeners' time and notifies them when a new episode is available.