WP Fastest Cache Premium – This plugin creates static html files from your WordPress. When the page is displayed, php and mysql are used. Therefore, the system requires RAM and a processor. If many visitors come to the site, the system uses a lot of RAM and processor, so the page is displayed so slowly. In this case, you need a caching system to not display the page again and again. The caching system creates a static html file and saves it. Other users reach the html static page.