XSLT Macro Engine is a custom macro engine used to render inline XSLT code snippets or external XSLT file locations.
<umbraco:Macro runat="server" Language="xslt">
<xsl:value-of select="$currentPage/@nodeName" />
</umbraco:Macro>
<umbraco:Macro runat="server" Language="xslt" FileLocation="xslt/MyAwesomeNavigation.xslt" />
The XSLT Macro Engine original started as a separate project, (see Our Umbraco for details.)