Supose that you changed the name of your domain and you want to take all your traffic to a new domain. Redirecting all your old urls to a new domain will not only help your users to know about it but also seach engine will know about it and start crawling it.

By adding the following 3 lines to the .htacces file in the root folder of your old domain will do the entire work for you:

RewriteEngine on

RewriteCond %{HTTP_HOST} ^domain.com$ [OR]

RewriteCond %{HTTP_HOST} ^www.domain.com$

RewriteRule ^(.*)$ "https://newdomain.com/$1" [R=301,L]