iTunes doesn't host any podcast files. You (as a podcast host) provide them an RSS link and when an end-user subscribes to your podcast, iTunes merely grabs you

iTunes doesn't host any podcast files. You (as a podcast host) provide them an RSS link and when an end-user subscribes to your podcast, iTunes merely grabs your RSS feed and has the end-user's phone download the latest episode from your servers. The episodes are stores and distributed from the podcast host's own server. The podcast app is just an RSS feed reader.