When you are writing an article for your blogger blog, you would want to display only a brief part of the article on home or any archive page. Also, you . would want the user to be able to read the entire article when user opens one. This is where Read More links come into play.
Read more links allow you to show a small part of article on home screen or any archive screen and when user clicks on it, the complete article is displayed. This is a functionality provided by all the major blogging platforms. Blogger provides this functionality too.