404 / Error pages
Under "404 / Error pages", you'll find broken links that visitors have clicked on. Based on this, you know exactly which pages need an update with a redirect link or similar fix.
Additionally, by clicking at the number under "referrers", you can see which pages are linking to these broken links besides direct links. These could be for example from an old campaign or a removed news article.

(Direct)- If the visitor enters the URL directly, clicks on a saved bookmark, or for example- follows a link from a conversation.