Ajax stands for Asynchronous Javascript & XML. It is a web technology through which a postback from a client (browser) to the server goes partially, which means that instead of a complete postback, a partial postback is triggered by the Javascript XmlHttpRequest object. In such a scenario, web-application users won't be able to view the complete postback progress bar shown by the browser. In an AJAX environment, it is Javascript that starts the communication with the web server.
Ajax technology in a website may be implemented by using plain Javascript and XML. Code in such a scenario may tend to look little complex, for which the AJAX Framework in .NET can be embedded in ASP.NET web applications.
In addition to XML & Javascript, AJAX is also based on DOM - the Document Object Model technology of browsers through which objects of the browser can be accessed through the memory heap using their address.
JSON - Javascript Object Notation is also one of the formats used in AJAX, besides XML.
So basically, in an AJAX-based web application, the complete page does not need to reload, and only the objects in context of ajaxification are reloaded.
Ajax technology avoids the browser flickering
