301 redirects are used to point both Google and humans to new page URLs, when old pages have been removed or renamed.
This does several things, it helps pass the value of the old page or post to the new one, it means that if the page was indexed in Google then anyone clicking on the search results doesn’t end up on a page that doesn’t exist.
It also means that any links already set up on your website are set to the new page, meaning that anyone visiting an old link is presented with a relevant page, rather than a 404.
