XHTML

The Extensible HyperText Markup Language, or XHTML, is a markup language that has the same depth of expression as HTML, but a stricter syntax.

XML:

An acronym for Extensive Markup Language, XML is the primary markup language format for storing structured data. XML is the most widely used for exchanging data between different systems.

XSLT:

Extensible Stylesheet Language Transformations (XSLT) is an XML-based language used for the transformation of XML documents.