What exactly is XML NameSpace

[wxdqz]

I just went thru <!-- m --><a class="postlink" href="http://www.jclark.com/xml/xmlns.htmCan">http://www.jclark.com/xml/xmlns.htmCan</a><!-- m --> anybody just explain the idea of XML Namespace? Are we talking aboutmaintaining a dictionary of <data> tags? What does the term xmlns:HTML="http://www.w3.org/TR/REC-html40mean? What is contained in the address mentioned above?Are we talking about some kind of standardization in the field of xml tagnames?Thanks in advance.Rohit