DEFINITION of 'Extensible Markup Language - XML'
A flexible markup language for structured electronic documents. XML is based on SGML (standard generalized markup language), an international standard for electronic documents. XML is commonly used by data-exchange services (like blog feeds) to send information between otherwise incompatible systems. Many other languages, such as RSS, are based on XML.
BREAKING DOWN 'Extensible Markup Language - XML'
Unlike HTML, XML allows users to define their own markup. Using XML, one user could choose to denote a footnote with the tag <footnote>, while another user could opt for <fn>. Using HTML, only one pre-determined tag can be used to denote a specific type of information. XML documents are meant to be easy to read since they contain user-defined tags and since the documents only consist of markup and content. Markup is the text that appears between two pointed brackets (e.g., <footnote>), and content is everything else.