[xsl] What do these expressions mean ?

["Z W" <mpc8250@xxxxxxxxx>]

Hi
XSLT newbie here.
What do each of these mean ?


<xsl:apply-templates select="sampleResult[generate-id() =
generate-id(key('group', @label)[1])]"/>


<xsl:template match="sampleResult">
      <xsl:value-of select="@label"/>
      <xsl:for-each select="key('group', @label)">

      </xsl:for-each>
<xsl:template/>


I like to incorporate this but I already have another for-each that
loops through the labels.

Many thanks