Asynchronous JavaScript and XML (AJAX) is a web development technique in which a web app fetches content from the server by making asynchronous HTTP requests, and uses the new content to upate the relevant parts of the page without requiring a full page load.
Read more: MDN

GajaxLib provides pre-defined function which makes making asynchronous HTTP request a piece of cake.

<script src="gajaxlib.js"></script>