What it does is very simple: it allows you to tag some html in your web page as title, and the web component will grab the text (skip html tags) and set it as document title. So you don't have to type the same text over again - and can avoid the risk of forgetting to update the document title, it will always show the same text as that displayed in the actual page.
A little more advanced is that you can use Polymer data binding (even if the component itslef does not depend on Polymer) to set the content of both the HTML tag and document title at the same time.
Tried to publish it on customelements.io but it seems like the job that updates the site is broken, so you can't see it there yet.