1) AJAX stands for Asynchronous JavaScript and XML. It allows web pages to update parts of a page asynchronously by exchanging data with a web server behind the scenes without reloading the whole page. 2) AJAX is based on open standards like JavaScript, XML, HTML and CSS. It allows for cross-browser and cross-platform applications. 3) The document discusses how AJAX uses the XMLHttpRequest object to send and receive data from a server asynchronously by HTTP requests in the background. This makes web applications more interactive and responsive.