AJAX, which stands for Asynchronous JavaScript And XML, is the use of several web technologies to achieve asynchronous communications with the server. To and fro exchange of data with a server/database happens without the need of page refresh. The term was coined by Jesse James Garrett in 2005.

jesse james garrett

AJAX methodology incorporates HTML, CSS, the DOM, XML/XSLT, JavaScript and the XMLHttpRequest object. Besides XML, data can also be interchanged with the server in JSON format.

Implementation of AJAX can be seen in popular websites like Youtube, Flickr, Gmail, Google Maps, Facebook.