This document discusses XML stylesheet language (XSL) which has two languages - XSL Transformation Language (XSLT) to convert XML documents to other formats, and XSL Formatting Objects Language (XSL-FO) to describe presentation of XML documents. It provides an example using an XML book document and XSL stylesheet to display book details by applying XSLT template rules and retrieving element values using <xsl:value-of> tags.