For a quick introduction to Extensible Styleshee Language Transformations you might want to check my introductory post here.
You should also check the resources in the MSDN website for the XSLT and XPath references.
Just to give you an idea of what XSLT can be though of, I’ll say that it is a programming language that allows you to parse an XML file and transform its contents into a tree that you can then utilise to manipulate that data. Hence the “transformations” in XSLT which is otherwise a more intelligent form of XSL.
