Asynchronous JavaScript and XML, commonly known as Ajax, is a technique used to make server requests outside of the normal page loading process. By utilizing GET and POST requests, additional data can be loaded after the initial page load by communicating with the server. This retrieved data is typically formatted in JSON or XML for processing on the client side.
To further understand the concept of AJAX, you can explore a demonstration using XML files in this link: http://www.w3schools.com/ajax/ajax_xmlfile.asp
I hope this information clarifies your understanding of Ajax and how it functions. Feel free to reach out if you have any more questions.