XSLT (eXtensible Stylesheet Language Transformation) is a language for specifying transformation of XML documents on the (usually) XML outputs, or text, HTML or other output formats.
The original application area, the transformation of XML data to XSL: FO (Formatting objects), thus rendering XML.
XSLT specification was therefore part of XSL (eXtensible Stylesheet Language).
Later, XSL set aside and began to be seen as a universal general description language XML-> XML (txt, HTML) transformations.
The current version is determined by the XSLT 1.0 specification. Work on version 1.1 have been pledged in favor of the development of XSLT 2.0.