Ans: Podcasting comes from iPod + broadcasting (though it seems like it should be called "ipodcasting", but maybe that's already been trademarked by Apple Computer ). The idea is cool: podcasters record a little "radio show" as an MP3 and make it available for download from their Web sites (usually, their blogs). You download the mp3 program, transfer it to your iPod or equivalent MP3 player, then you can listen to the dulcet tones and insightful commentary of your favorite bloggers while on the train, bus, bicycling, exercising, whatever.
Now take the additional step of having a program that watches all of your favorite podcasting sites and automatically downloads any new podcasts directly to your computer (or MP3 device, iPod, what-have-you) just as an RSS aggregator helps you keep track of dozens of different Weblogs and RSS-friendly Web sites. Making this even more interesting, some innovative folk have found out that you can utilize some of the Voice over IP (VOIP not yet picked up in India) systems to actually use your telephone as a recording device (after all, it has a pretty good voice-frequency microphone) so you can ostensibly get started with almost zero investment. All you need are two critical components: something to say, and someone to download it and listen to your program. But there are some terrific audio programs available, many from existing radio personalities and radio shows.
There are a few independent broadcasters who are making a name for themselves in the podcast world too, notably Adam Curry. A good place to learn more about what's out there is to go through the directory at iPodder.org. There's some good stuff out there!