AJAX stands for Asynchronous JavaScript And XML. It is based on JavaScript and HTTP requests.
Ajax is a catchy name for a type of programming made popular in 2005 by Google and other big web developers.

The Ajax technique accomplishes by using the following technologies:

•  JavaScript that allows for interaction with the browser and responding to events
•  The DOM for accessing and manipulating the structure of the HTML of the page
•  XML, which represents the data passed between the server and client.
•  An XMLHttpRequest object for asynchronously exchanging the XML data between the client and the server.

The following graphic shows how these technologies work together to update a piece of a page with new data from the server.

•  AJAX is not a new programming language, but a technique for creating better, faster, and more interactive web applications.
•  With AJAX, your JavaScript can communicate directly with the server, using the JavaScript XMLHttpRequest object. With this object, your JavaScript can trade data with a web server, without reloading the page.
•  AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole pages.
•  The AJAX technique makes Internet applications smaller, faster and more user-friendly.
•  AJAX is a browser technology independent of web server software.

•  XHTML and CSS standards based presentation
•  Interaction with the page through the DOM
•  Data interchange with XML and XSLT
•  Asynchronous data retrieval with XMLHttpRequest
•  JavaScript to tie it all together

•  Form driven interaction.
•  Deep hierarchical tree navigation.
•  Rapid user-to-user communication.
•  Voting, Yes/No boxes, Ratings submissions.
•  Filtering and involved data manipulation.
•  Commonly entered text hints/autocompletion.
•  Long Running Queries/Remote Calls
•  Computationally Expensive Operations
•  Server Savings
•  Interactive Panning And Moving Over Data