The tutorial is on adding a new Webmaster user role which comes in between your site Administrator and Editor. This user is same as site Administrator but it excludes some capabilities like managing plugins, changing themes. Users with this role will not be able to install or activate any theme or plugin. They can change the widgets, edit theme options like background, header images etc if your theme provides and do all other things which a site admin does.
Role Scoper, a free WordPress plugin allows you to gain more control over reading and editing permissions in your WordPress site. Using this plugin you can assign restrictions and roles to your specific WordPress pages, posts and categories.
Sometimes when you make changes to any of your blog post and think of reviewing them before making them live, using default WordPress features what you can get is post revisions from the author and then upload them manually. But with Revisionary plugin you get option to save revisions to your published post and then they can get reviewed, then published later.
There are many different plugins in WordPress Plugin Repository that allows you to limit your website access in different ways. Now this tutorial explains you limiting your WordPress site access for logged in or allowed by IP addresses.