Redirects are pages that direct users to other pages. Why is this useful? Well, there are various reasons why you might change a URL. By redirecting an old URL to a relevant new one, you can still provide the website visitor with content.
Additionally, there might be cases where a page might no longer exist in the future, even though you've put a lot of effort into link-building. In that case, you can use Dock > Tools > Redirect to enter your old URL and specify the page it should redirect to. This way, you retain all your SEO investments.