An XSL transformer will transform in the following way:
Template specifies transformation rules. A Stylesheet document can be made up of at least one template, which acts as an entry point. Every template uniquely identifies a particular node in the source tree.
XPath is an expression language used for addressing parts of an XML document. XPath is used to navigate through elements and attributes in an XML document.
XSL-FO deals with formatting XML data. This can be used for generating output in a particular format like XML to PDF, XML to DOC, etc.