This web part renders "canonical" link to a page, which allow search enginges find "right" link to the page.
This web part is very useful for SEO. It renders special tag, which tells to search engines "right" link to the page.
You can get more details about the tag here: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=139066#2
and here: http://wiki.whatwg.org/wiki/RelExtensions
Link rendered by the web part consist of the following parts:
- Canonical domain name. The web part uses default domain name of the site, or a value of "Canonical Domain Name" parameter.
- Document URL as it rendered by the CMS engine (usually based on document alias path).
- Optional, "lang" parameter, which specify document culture.
You can also define custom field named "Canonical" for any document type and the web part will use its value.