W3C technology for transforming and formatting XML
split into the two separate standards – XSLT and XSL-FO
XSLT (eXtensible Stylesheet Language)
describes transformation from XML to another XML, HTML or plain text
uses XPath as a query and expression language
XSL-FO (Formatting Objects)
set of abstract objects that can be used to specify visual appearance of document
can be expressed in XML (and thus generated by XSLT)
you can imagine it as HTML that is oriented towards print output with more control over layout and appearance