Podcasts are pre-recorded audio files. Usually they are in MP3 format. They are not live broadcasts. Listeners typically download them and then load them onto their iPods, MP3 players, or other portable media devices for later listening. Because podcasts are mostly spoken word, the MP3 files can be created at a lower fidelity than music MP3s, hence deliver a considerable amount of audio content with surprisingly small file sizes.
People listen to podcasts when and where they traditionally listened to radio or music: during their daily commute, at the gym, or on airplanes. Unlike radio, there is no constant dial searching. A podcast listener is usually committed to listening to the full show.
A compelling podcast can be created quickly, simply, and with little to no investment in hardware and software. All one needs is a computer, a simple microphone, and audio recording/editing software. Inexpensive and even free recording/editing software like Audacity can be downloaded from the Internet.
After creating your podcast, the MP3 files are hosted either on your own Internet site (or a third party site that specializes in podcast hosting). A simple RSS/XML file is also hosted on your site. The RSS file allows iTunes and other podcast aggregators to link to your MP3 and distribute it. Of course, one does not need to register or link via iTunes. An RSS file for a podcast intended for internal company communication can be accessed by employees outside of iTunes and other public podcast aggregators.