Axes in XPath (which we will describe shortly) provide an indication of the direction we, or an XPath processor, are to travel around the tree representation of an XML document.
Axes can be viewed as being forward—that is, in document order—or reverse—that is, in the opposite direction of document order.
The direction of an axis that forms part of a location step influences how any position in a predicate in that same location step is interpreted.
In a forward axis, a predicate  means that the second node in document order is selected.
<SEUsingXML> <Chapter>The XML Jigsaw Puzzle</Chapter> <Chapter>The Basics of XML</Chapter> <Chapter>XML Building Blocks</Chapter> <Chapter>Structuring XML Documents ...