page rules are rules that permits to apply a permanent redirection for a page or a group of page.
With the below rule:
If a page called database:table does not exist, the router will calculate the target page db:table and if the page exists, it will rewrite it.
With the below rule:
If a page called dokuwiki:404managerplugin does not exist, the router will send a permanent redirect to the page https://combostrap.com/url/manager