Ajax & Web 2.0

In a previous life, I did computers for a living. Maybe that's why I've been curious about what Web 2.0 is (i.e., not what it does). In a discussion of Ajax, I found this snippet:

"Ajax's most appealing characteristic, however, is its “asynchronous” nature, which means it can do all of this [send and receive info from a server script] without having to refresh the page. This allows you to update portions of a page based upon user events and provides one of the cornerstones of Rich Internet Applications (RIA) referred to in discussions of “Web 2.0.” "

-- Web Design in a Nutshell (O’Reilly Media, Inc., third edition, February 21, 2006)

No, it's not a lot of info and it doesn't explain how to do it (that's in the rest of the article), but it seems my curiosity is satisfied.