While it would have been possible to write straight HTML code to load the CSS file by registering a function with the wp_head action hook, as we have done previously, WordPress has utility functions designed to help avoid loading duplicate style sheets or scripts on a site. In this specific example, wp_enqueue_script is used to place the plugin's style sheet file in a queue that will be processed when the plugin header is rendered, with the associated name privateshortcodestyle. Once WordPress has processed all the plugins and boiled down all the style sheet requests to single instances, it will output the necessary HTML code to load all of them.

The content of the stylesheet.css file is normal CSS code that specifies that any text that is assigned the private class should be displayed in gray, while the text displayed to non-registered users should be displayed in white on a red background.