It's a fact of life that XML, which stands for eXtensible Markup Language, is invading our lives more and more as programmers, and I feel this is a good thing. The reason being XML has the ability to cross all sorts of boundaries, and probably the only chance we have to obtain a truly independent, cross-platform data transfer format.
A parser is a piece of software that makes sure the XML document is valid or at least well-formed. Parsers are extremely complex to develop and so only experienced programmers will design one. Once a parser is developed, other programmers and Web designers can easily reuse it .A parser is part of XML that you will never see.
XML tags are custom-defined thus enabling the generation of domain specific markup languages for diverse fields such as vector graphics, mathematics, music and technical documentation. I hope my now you have got a fair idea of this most hyped up XML technology, we will explore more of this in the next part.