Think how a desktop aggregator works. You subscribe to a set of feeds, and then can easily view the new stuff from all of the feeds together, or each feed separately.

Podcasting works the same way, with one exception. Instead of reading the new content on a computer screen, you listen to the new content on an iPod or iPodlike device.

Think of your iPod as having a set of subscriptions that are checked regularly for updates. Today there are a limited number of programs available this way. The format used is RSS 2.0 with enclosures.

In the future, radio shows like All Things Considered and Rush Limbaugh will be available in this manner, and perhaps other syndication formats will support enclosures.