The only real difference between a podcast and a regular sound file is that podcasts are generally distributed via syndication. You sign up for (subscribe to) a podcast, much like you would to a blog, and special (free) software helps you configure your computer to automatically download audio content, or alert you when new podcasts are available from the sites to which you've subscribed. One of the most common podcast subscription software is iTunes (free and you don't need to own an iPod to use it), but other RSS feedreaders can also help you manage the podcasts that interest you.
There are a number of genealogy podcasts that offer ongoing content of interest to just about anyone who loves family history. The Genealogy Guys have recorded over 125 podcasts over the past several years, and continue to offer new ones on a regular basis. DearMYRTLE's Family History Hour has also been broadcasting on the Internet for several years, with archived podcasts available online back to September 2005. Lisa Cooke is just celebrating her 1 year anniversary of the Genealogy Gems Podcast. These and other current genealogy podcasts that I enjoy are included in my list of 7 Genealogy Podcasts to Enjoy.
In addition to the currently broadcasting genealogy podcasts, there are also several that no longer appear to be in production, but still offer an excellent amount of archived podcasts online. One of the best of these is Family Roots Radio. Genealogy On Demand and Under the Tree (African American genealogy and history) also have many archived treasures. There are also numerous podcasts, such as the Genealogy Tech Podcast, that offer outstanding content, but either publish irregularly or have only a few podcasts available online.
If all of this talk of RSS and syndication is confusing, don't worry. Podcasts are really as easy as clicking on a link to download an audio file to your computer. Just as with a blog, you don't have to subscribe to access the content. Just visit the Web site of your favorite podcast whenever the mood strikes you to see what's new!