A string variable containing the URL to the "permalink page" or "individual page" for this article.
The "permalink page" or article page" for an article is a page that is meant to contains only that article and related information. In the default article template, this page includes the article title and body, its comments and its trackbacks.
Example
In the example below, the words "Permanent link to this entry" are linked to the "permalink page" for this article.
<a href="{{permalink_url}}">Permanent link to this entry</a>