Here I am going to explain this trick with an example. Suppose I have a blog post with link www.corenetworkz.com/article-publish.html but accidentally I have changed its link structure. Consider its new link structure as www.corenetworkz.com/new-article-publish.html and it is live. There is no way to return to the old link structure but I don't want to loose the backlinks pointing to the old post. In this situation, I can use this new blogspot trick to perform 301 redirection to new link from the old link. Google spiders will treat the old post and new post as same.

This article tells how to send users from old broken blog post links to new working posts. Similarly following article tells steps to set custom domain name for your blogspot blog. To read more about it, follow the link below.
How to Setup Custom Domain Name For a Blogspot Site

After setting up a custom domain, most of the users face the issue of redirecting the blogger blog with wwww version and without www version. We fixed the issue by following the steps provided in the link below.