why to use 301 redirect code example

Example 1: 301 redirect

301, "Moved Permanently"—recommended for SEO
302, "Found" or "Moved Temporarily"
Meta Refresh

Example 2: how to create a 301 redirect with domain.com

RewriteEngine On 
RewriteCond %{HTTP_HOST} ^DOMAIN.com [NC]
RewriteCond %{SERVER_PORT} 80 
RewriteRule ^(.*)$ https://www.DOMAIN.com/$1 [R=301,L]