Now we are getting some great insight and writing about how this is done.
Quoting Jesse James Garrett:
Take a look at Google Suggest. Watch the way the suggested terms update as you type, almost instantly. Now look at Google Maps. Zoom in. Use your cursor to grab the map and scroll around a bit. Again, everything happens almost instantly, with no waiting for pages to reload. Google Suggest and Google Maps are two examples of a new approach to web applications that we at Adaptive Path have been calling Ajax.Again, all credit to the link which led me there:
fundamental shift in what’s possible on the Web. Ajax isn’t a technology. It’s really several technologies, each flourishing in its own right, coming together in powerful new ways.
Preoccupations: "Ajax, who he?"