An XML feed is a plain text version of your website that is perfect for sharing between other applications and using on websites. It also makes editing content between designers, web teams and anyone else who may have input in the end product simple.

Furthermore, if your XML feed is used on another website, your content will be exposed to their audience as well, creating new traffic for your site. This is because clicking on any of the links will bring them to your site, resulting in new views. Using XML will allow your content to be published quicker as it’s not being reformatted and adjusted in between each stage of completion. Consider it to be a universal language between everyone who works on your web-based project.

This article offers a great explanation of XML's many uses.