XML is an acronym for "Extensible Markup Language". XML is the latest, powerful , platform-independent and content-dependent technology in the internet development. Learn all about it here.
XML is still under development stage. It is evolving beyond the draft specifications put forward by w3c. These changes may be rapid and keep yourself updated by visiting related sites. Discussion about XML namespaces, schema, style sheets and XQL - a developing query language are beyond the scope of this introductory article.