What is 301 redirect?
 

A 301 redirect is a page status code that tells search engines a page has permanently moved to another URL. The new URL might be on the same site or on a different one.

301 is the term which tells search engine which page has to be redirect permanently to another url.

The HTTP response status code 301 Moved Permanently is used for permanent redirection.

301 redirect is the process of permanently moving from old url to new url for the following reasons :

Website Redesign
Move to new domain
Web page which doesn't exist

301 Redirect is used to permanently move the site to a new location. Google does not penalize for this redirect.

301 redirection is used when we have to move a website permanently.The main advantage from this redirection is we can save traffic and old seo work after movement too.