 <p><strong>XLS</strong> is either a typo for <strong>XSL</strong> or a reference to Microsoft's <a href="https://products.office.com/en-us/excel" rel="nofollow">Excel</a> spreadsheet <a href="https://en.wikipedia.org/wiki/Microsoft_Excel#File_formats" rel="nofollow">format</a>.</p> <p><strong>XSL</strong> <a href="https://www.w3.org/Style/XSL/" rel="nofollow">refers</a> to a family of W3C recommendations related to XML transformation and presentation:</p> <ul> <li><strong><a href="https://www.w3.org/TR/xslt" rel="nofollow">XSLT</a></strong>: A language for transforming XML documents.</li> <li><strong><a href="https://www.w3.org/TR/xpath/" rel="nofollow">XPath</a></strong>: A language for addressing parts of an XML document.</li> <li><strong><a href="https://www.w3.org/TR/xsl/" rel="nofollow">XSL-FO</a></strong>: An XML vocabulary for specifying formatting.</li> </ul>