A file with the XSLT extension is an Extensible Stylesheet Language Transformations . It’s a language that uses XSL instructions to transform and style an XML file.
XSLT File,How XSLT Files Are Used
XSLT File,An XSLT is a text file and provides rules that an XML file should follow. Among other functions, XSLT can be used for sorting and arranging different parts of the XML and hiding some elements from displaying altogether. W3Schools.com has some XSLT examples you can look at.
When XSLT files are used with XML files, the original XML file isn’t altered in any way. Instead, a new XML file is created. In fact, XSLT files can be used to “transform” not only XML files, but also many other structured documents.