The self axis selects the context node. : self « XPath « XML Tutorial

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2. XPath
3. self

The unabbreviated syntax for the selfaxis is as follows: 

self::node() 

The abbreviated syntax for the context node is the period character. 
To select the value of the context node using the xsl:value-of element, you would write the following: 

<xsl:value-of select="." /> 

The unabbreviated syntax is as follows: <xsl:value-of select="self::node()" /> 

File: Data.xml

<?xml version = "1.0"?>
<product>
   <books>
      <book>
         C++
      </book>
      <book>Java</book>
   </books>
</product>

File: Transform.xslt
<?xml version = "1.0"?>
<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/product">
    Self for
    <xsl:apply-templates select="book" />
  </xsl:template>
</xsl:stylesheet>

Output:

<?xml version="1.0" encoding="UTF-8"?>
    Self for