A 301 redirect through htaccess is necessary when we have a page that we have recently updated, for example the site was previously made in plain html (or it can be xthml, flash or whatever) and now we migrate the site to a content manager (whatever you want).
So from the outset all the URLs are going to change, where before they were called www.mydomain.com/us.htmlnow it is called www.mydomain.com/us
To change it, the best option if you are on a Linux server (90% of servers with web output), the ideal is to modify the .htaccess file (make sure the file is not hidden and can be edited).
Then just add a few lines and that's it
redirect 301 /old_url.html http://www.mydomain.com/new-url/
Be careful, it is important to only put /url_antigua.html and not the complete domain, then in the second part for example in http://www.midominio.com/url-nueva/ there you can even change the domain if you web page is called something else.
Do you want to know more about redirects that are not penalized by Google? To know more about 301 redirects and other things you can consult us at http://www.masclicks.com.mx/consultoria
Or watch the following video
