A master template is a basic page layout that includes elements you would like to have appeared on multiple pages. Creating a master saves you the bother of setting up a basic layout on several different pages.
Rvsitebuilder 7 allows you to create a master template for a system page. The layout and content for header, footer and sidebar sections stored in the Master Template are copied over to Register and Login pages. When you modify the Master Template, the changes cascade to all other system pages on your site.