XML is a universal language for data on the web that lets developers deliver content from a wide variety of applications to the desktop. XML promises to standardize the way information is searched for, exchanged, adaptively presented, and personalized. XML is known as Extensible Markup Language which has the concept of rule-specifying tags and the use of a tag-processing application.

The design goals for Web Development using XML are
 XML shall be straight forwardly usable over the Internet ;
 XML shall support a wide variety of applications ;
 XML shall be compatible with SGML ;
 It shall be easy to write programs, which process XML documents ;
 The number of optional features in XML is to be kept to the absolute minimum, ideally zero ;
 XML documents should be human-legible and reasonably clear ;
 The XML design should be prepared quickly ;
 The design of XML shall be formal and concise ;
 XML documents shall be easy to create.

Why XML
XML is now a standard for data interchange, so you may need to pass your data on to others as XML or take XML as input. There are advantages over many competing technologies. It is essential technology for anyone looking for more efficient and cost effective ways of both managing and transfering data.

XML is easy to convert further into different formats as required: e.g. HTML, PDF, and plain text. In Web applications, XML is also used to reduce server load and hits.