Ajax is ubiquitous. Look around at fackbook, twitter, gmail, outlook web, google maps, google instant search, whichone isn’t utilising Ajax?
The basic idea of Ajax is to use XMLHttpRequest to transfer data asynchronously. Of course, you can also do this in a synchronous way.
The use of Ajax in Web development architecture vs. the traditional method:
When did Ajax come out?
In 2005, Jesse James Garrett coined this term in the article Ajax: A New Approach to Web Applications. The technique came out for many years as a way to avoid reloading the whole web page for better user experience.
How Ajax works?
Browsers are implemented differently, and hence the support of XMLHttpRequest is not fully done. There are many libraries to help in writing Ajax such as jQuery, backbone, YUI, or other big web frameworks like Angular, Dojo. Essentially, they try to detect the client browser and adopt the different underlining implementation of the XMLHttpRequest API.