XPath is a syntax for defining parts of an XML document. XPath uses path expressions to navigate in XML documents. XPath contains a library of standard functions. XPath is a major element in XSLT. XPath is a W3C recommendation.

XPath is used to navigate through elements and attributes in an XML document. XPath is a major element in W3C's XSLT standard.

http://www.w3schools.com/xpath/xpath_intro.asp