XML is about defining data. With XML you can define documents that are understood by computers.
But to make these documents understandable to humans, you need to show them.
It works just like adding styles to HTML elements.
The preferred solution is using XSL (eXtensible Style sheet Language). XSL can convert XML documents into HTML.
It can be used client side but the best solution is to use XSL server side. You can convert your XML documents to HTML, thus making them visible to any browser.