The eXtensible Markup Language
Enables structured documents to be served, received
and processed on the Web
A markup language is a language for structuring a
flat document through the addition of tags. Tags behave
as labelled brackets.
This is a trivial example.
XML is a meta markup language, it gives a way of
describing new markup languages and documents.
This is an XML Document Type Definition
(DTD) describing the XML language of the previous example.
XML is standard. It is a streamlined
version of the Standard Generalized Markup Language (SGML).