XML (extensible markup language) is similar to HTML (Hypertext Markup Language), but unlike HTML tags, XML tags are unlimited and self-defining. A simple tutorial for Handling XML with Ajax might be very helpful.
The XMLHttpRequest object is the piece of the puzzle that allows Ajax applications to run asynchronously. Using the XMLHttpRequest object, an Ajax developer can program applications that are capable of exchanging data between the client and the server behind the scenes, without requiring a new page refresh for each data request individually.
If you found this page interesting you may want to read more from our Ajax tutorial.