Redirection is process of forwarding one URL to a different URL. There are three main kinds of redirects online; 301, 302 and meta refresh.
301 ('Moved Permanently') - Recommended for SEO
302 ('Found' or 'Moved Temporarily')
Meta Refresh
In some cases, it may be possible to maintain the URL structure of a new website, but if the content is changing it often makes sense to change the URL along with it. This is where the 301 redirect comes into play. It tells the search engines that the old page has been moved to a new URL and no longer exists. The 301 redirect also sends a website visitor to the new page automatically.
A huge search engine ranking factor is trust. The search engines favor websites that are aged and have relevant inbound links pointing to it. Without implementing the 301 redirect from an old page to the new page, to the search engines the new page is brand new, when in fact, it isn’t. A page that is considered to be brand new will basically be starting over, whereas a 301 redirect can maintain some of the power and credibility of the old page. A 301 redirect may not pass all of a web page’s link power to the new page, but it’s the best way to try and maintain as much power as possible.