Asynchronous JavaScript and XML (AJAX) is not a technology in itself, but is a term that describes a “new” approach to using a number of existing technologies together, including: HTML or XHTML, Cascading Style Sheets, JavaScript, The Document Object Model, XML, XSLT, and the XMLHttpRequest object. When these technologies are combined in the AJAX model, web applications are able to make quick, incremental updates to the user interface without reloading the entire browser page. This makes the application faster and more responsive to user actions.
The two features in question are that you can:
- Make requests to the server without reloading the page
- Parse and work with XML documents
A good example of a site using AJAX is www.netvibes.com and maps.google.com