AJAX calls are asynchronous, meaning they’re made behind the scenes, independently from each other and the site as a whole. When a browser makes an AJAX call to the server, it isn’t stuck waiting for a response, halting all of the site’s functionality. Instead, the web service on the server will send the data back to the browser once the task is completed, where client-side scripts will process the response and deliver it to the user.
For example: If you want to give a movie on Netflix a star rating, you can click the rating, it will show up immediately, and the rating gets stored in your profile, all without any other changes to the page. That’s AJAX in action.
Pre-AJAX, the rules for client calls to the server—basically, anything the browser requests from a database to make a site responsive—were “postbacks,” plus server-side processing. Post-AJAX, the browser can “callback,” requesting small amounts of data directly from the server—all without needing to wait for a postback.
MindIQ offers a comprehensive curriculum of courses in XML and related technology, including courses in using XML from Java applications, and courses in SOAP/WSDL Web services.