That means if someone types the URL of your blog, they automatically see the newly rearranged look. It changes the design heavily and was meant to let people read the blog in more than on design. Until now, you had to initiate the view as a reader. Now the blogger itself can choose to show that look to all people. But keep in mind, it breaks your AdSense integration on the frontpage. Which means no ads at all. But they will appear if you click the article.
It sure makes sense for some people. I changed the look for my microblog "MicroRyo". You can head over to see how it looks like.