XSLT is a language for transforming XML documents into other formats like HTML, text, and PDF. The document lists over 30 elements used in XSLT like <xsl:apply-templates> to apply templates based on node type, <xsl:copy> to copy nodes, and <xsl:template> to define reusable templates for generating output. Elements provide functionality for conditional processing, importing/including other XSLT files, generating output, and passing parameters between templates.