301 Redirect
This is normally used 2 ways. If you have had a new website built and you are looking to preserve your current page rankings and keywords, you will re-direct an old page URL to the new page URL – as an example:
Old: https://www.website.com/services/webdesign/
New: http://www.website.com/webdesign/
The old URL would re-direct to the new one to keep the integrity of links coming into the page, so they can be redirected to the new page without creating a 404.
The second use of a 301 redirect is to use a domain that might have expired or is currently for sale that has good domain authority. By following the correct steps to set up a domain 301 redirect, it can be very beneficial as it will pass the domain authority onto your main website, thus in turn giving your own website a higher authority than it did before.