The document discusses how to use XSLT transformations in Mule applications. XSLT can transform XML payloads from one form to another. In Mule, this is done using the XSLT transformer component. The example shows a flow that receives an XML payload, sets the payload, then transforms it using an XSLT file. The XSLT file contains templates to select nodes from the source XML and output them in a new structure to a target XML payload. Hitting the endpoint URL transforms the payload as defined in the XSLT file.