XSL Transformations
Chapter 17 of the XML Bible. The transformation language provides elements that define rules for how one XML document is transformed into another XML document.

XSLT Tutorial
With XSL you can freely modify any source text. Stylesheet 1 and Stylesheet 2 produce different output from the same source file.

XSLT Tutorial: Basics and First Example Application

In order to present XML documents or data to the user in an attractive way in browser, mobile phone or PDF format, the original data must first be converted to the necessary formats. This is the purpose of XSLT as part of the style component of XML.

Understanding XSLT

Without knowing a little XSL, it's pretty difficult to understand some of the frequently touted advantages of XML.

Top XML: XSLT Tutorial
When we are working with XSLT, the context for a query is the node in the source XML document currently being processed. So in the template xsl:template match="/", we are in the context of the root of the XML document. This isn't the PEOPLE element, it's the whole document, above the PEOPLE element.