AJAX

AJAX stands for Asynchronous JavaScript and XML. AJAX is not a new technology; it is a new way of combining existing technologies. AJAX is create an asynchronous request to the web server using client-side JavaScript and an XmlHttpRequest object, and map a function to be executed when the response is received. An asynchronous request means that the browser does not need to wait for the response after sending the request to the server. we get this by sending a request to the web server for a small amount of information, as many times as we want, without sending the complete information on the form. In AJAX, the request is for data, not for a GUI element, so an AJAX request can be handled by an ASP.NET page without any HTML content, a custom HTTP module, or a web service. The core component in AJAX is the XMLHTTPRequest object.

XMLHTTPRequest

The XMLHTTPRequest object is used to send a request to, and receive a response from, the web server. Using this object, the web page can make a request to the web server asynchronously, and receive a response asynchronously

Advantages of AJAX:
1-It increases the richness of web page userinterface.
2- Avoid extra load on server