What is XML?
In the shorted terms, XML is a type of markup language. XML stands for EXtensible Markup Language. The benefit of XML is that it defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. It is a W3C Recommendation, which basically means that it is recommended by the World Wide Web Consortium (W3C), which is the main international standards organization for the World Wide Web.
XML is quite similar to HTML in nature, and was designed to store and transport data, while also being designed to be self-descriptive. XML is designed for simplicity and generality, as well as for usability across the Internet.
RSS, Atom, SOAP, SVG, and XHTML have all been developed using XML syntax, which has also become the standard for many office-productivity tools, including Microsoft Office (Office Open XML), OpenOffice.org and LibreOffice (OpenDocument), and Apple's iWork.