XML is short for Extensible Markup Language. It is a specification that was developed by W3C. XML is a pared down version of SGML. It is designed especially for web documents. XML is a metalanguage that allows users to define their own customizable markup language. This is especially important when attempting to display documents on the internet. XML is an important term to know. XML was basically made to store and transport certain data. It defines the set of rules for encoding documents that is readable by both machines and human beings. XML is very important for webmasters and a term everyone should know.