Just What is XML Anyway?

XML is an acronym for eXtensible Markup Language.  Like its predecessor Hyper Text Markup Language, or HTML, it has its root in a standard known as the Standard Generalized Markup Language, or SGML.  To understand why we need XML, let’s take a look at both SGML and HTML.  Understanding their respective strengths and weaknesses will shed some light on why XML exists and why it is gaining such strong momentum.