AJAX, or Asynchronous JavaScript and XML, is a web technology that is based on JavaScript and HTTP requests. By using AJAX we can use JavaScript to get/send data from/to a server without reloading the whole webpage with the help of XMLHttpRequest object. 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 data received from web server is in XML format, and then we use JavaScript to parse that XML and do something useful with it.

AJAX works with any server-side technology, including PHP, Perl, ASP (.NET), Python, Ruby, ColdFusion, SSI, JSP, etc. So by using AJAX you can make your webpage dynamic, smaller and user-friendly. Also you can place ‘rich media contents’ on your webpage.