XML stands for Extensible Markup Language, was defined by the
XML Working Group of the World Wide Web Consortium (W3C). This group
described the language as follows:
The Extensible Markup Language (XML) is a subset of SGML…Its
goal is to enable generic SGML to be served, received, and processed
on the Web in the way that is now possible with HTML. XML has been
designed for ease of implementation and for interoperability with both
SGML and HTML.

As you can see, XML is a markup language designed specifically for delivering
information over the World Wide Web, just like HTML (Hypertext Markup
Language), which has been the standard language used to create Web pages
since the inception of the Web. Since we already have HTML, which continues
to evolve to meet additional needs, you might wonder why we require a com-
pletely new language for the Web.