XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (510 page)

AnyKindTest	node ( )
NodeName	QName| *
TypeName	QName

A
KindTest
is used to define the kind of node that is required and, optionally, information about its schema-defined type.

Let's take the simple cases first:

• text()
  matches any text node.
  
• comment()
  matches any comment node.
  
• node()
  matches any node whatsoever (but remember that on its own, it means
  child::node()
  , which searches only for nodes that are children of something).
  
• processing-instruction()
  matches any processing instruction node.
  
• processing-instruction(NCName)
  matches any processing instruction node with the given name (the name of a processing instruction is referred to in the XML Specification as the
  PITarget
  ). For compatibility with XPath 1.0, the
  NCName
  may be written in quotes as a
  StringLiteral
  .
  
• document-node()
  matches any document node.