AJAX - Sending a request to a server

xmlhttp.open("GET","date.php",true);
/*It has been assumed here that date.php is in the same directory.*/
xmlhttp.send(null);

The open() method takes three arguments as described below -

• First argument – The method to use while sending request to the web server i.e. GET or POST.
• Second argument – URL of the server side script
• Third argument – Boolean to specify whether the request should be handled asynchronously or not.

 
The send() method is used to the request to the server.

source:http://www.botskool.com/programming-tutorials/ajax-tutorials/ajax-basic-tutorial