|Chapter 18 - Ten Most Confusing Things About XSLT|
|XSLT For Dummies|
|by Richard Wagner|
|Hungry Minds 2002|
XPath is used to create expressions, but some types of expressions are more important to XSLT than others. In a generic sense, an expression is a string of XPath instructions that the XSLT processor evaluates to produce a result, which may be a number, string, Boolean value, or a node set. However, XSLT is most interested in a particular kind of expression called a location path , which is a set of instructions that specify what nodes to bring back to the XSLT stylesheet. The location path then consists of a series of smaller parts called location steps. A location step consists of an axis, a node test, and an optional predicate and takes the following form: axis::nodetest[predicate] .
Check out Chapter 5 for more details on XPath expressions.