XML (Extensible Markup Language)

Stands for "Extensible Markup Language." (Yes, technically it should be EML). XML is used to define documents with a standard format that can be read by any XML-compatible application. The language can be used with HTML pages, but XML itself is not a markup language. Instead, it is a "metalanguage" that can be used to create markup languages for specific applications. For example, it can describe items that may be accessed when a Web page loads. Basically, XML allows you to create a database of information without having an actual database. While it is commonly used in Web applications, many other programs can use XML documents as well.

Definition from the Tech Terms Computer Dictionary
http://www.techterms.com/definition/xml