XHTML eXtensible HyperText Markup Language. HTML re-written as an application of the XML language. See the W3C Working Draft: Building XHTML Modules
XML (Extensible Markup Language)
XML is the Extensible Markup Language, a system for defining specialized markup languages that are used to transmit formatted data. XML is conceptually related to HTML, but XML is not itself a markup language. Rather it's a metalanguage, a language used to create other specialized languages.
