You need some template skills to be able to use this add-on.
If your website generates a lot of Page Not Found pages it's probably a good idea to help your visitor find what they were looking for.
Imagine that your visitor enters http://www.somewebsite.com/blog/concrete5. Unfortunately the site has been rebuilt and the path doesn't exist anymore. The visitor now sees a "Page Not Found" page.
This add-on shows a list of page suggestions for the visitor based on the URL. In this case the add-on will search for pages that relate with "blog" or "concrete5".
The add-on is in English and comes with Dutch and German translations. It has been tested on PHP 5.3, 5.4, 5.5, 5.6 and 7.0.
Example 404-page with Elemental theme: