Recursive processing

<xsl:apply-templates select="node-set expression" .../>

apply pattern matching and template instantiation on selected nodes (default: all children);
mode="..." on xsl:template and xsl:apply-templates allows an element to be processed multiple times in different ways

<xsl:call-template name="..."/>

invoke template by name (name="..." on xsl:template)

<xsl:for-each select="node-set expression"> template </...>

instantiate template for each node in node-set (document order by default)

The value of a select attribute is basically an XPath expression evaluated with the current node and current node list as context.