XML is the file extension of a type of file format called Extensible Markup Language, which is used to store information in a structured format. The XML format is used extensively for the Web, as well as other applications. HTML, for instance, is the file format used for creating web pages and is based upon the XML format. Starting from Microsoft Office 2007, Microsoft Office uses the XML-based file formats, such as .docx, .xlsx, .pptx, and so on.