XML stands for the Extensible Markup Language, and it is a new 'language' that is being used on the Web for data interchange and for Web page presentation. Just as with HTML, XML describes a set of objects that are used to create applications on the Web. Documents stored in an XML format have built-in immunity to incompatible changes like this. XML mirrors HTML in this way by providing a clear text syntax that describes the Web page and the data associated with the page.
Programming languages contain detailed lists of instructions for a computer to perform.
An XML document is essentially a specially formatted description of a person, place, or thing. In this respect, it closely resembles HTML, the language of most web pages today. Instead, future Web designers will use XML, HTML, Java, and more to implement more sophisticated Web sites. Because XML is a 'standardized' language, and is human readable, many developers have started using XML to share data between applications over the network. Applications that need to export or import data expect to see the data in a specific way, and XML provides the mechanism to make sure this happens.