If you would like to break up your blog posts into a brief introduction or a preview paragraph with a link to “read the rest of this entry” you use the “More Tag”. It is on the toolbar where you write your blog post.
This can help keep your blog’s home page less cluttered, especially once you start having lots of posts.
The downside is that for the first paragraph or two, you need to setup the post and make the reader want to click the “read the rest of this entry” link. If the intro paragraph isn’t good enough, they may not click through.
Mike