A transformation is specified by a "stylesheet" or "transform" document:
<xsl:stylesheet version='1.0' xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <!-- your rules here --> </xsl:stylesheet>
or
<xsl:transform version='1.0' xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <!-- your rules here --> </xsl:transform>
The choice of 'stylesheet' or 'transform' has no affect on the outcome according to the XSLT recommendation.
Applications may interpret 'stylesheet' differently from 'transform' in terms of:
whether they run the transformation
what they do with the results.