WP Fastest Cache Premium plugin creates static HTML files from your dynamic WordPress blog. When a page is rendered, php and MySQL are used. Therefore, the system needs RAM and CPU. If many visitors come to a site, the system uses lots of RAM and CPU so the page is rendered so slowly. In this case, you need a cache system not to render the page again and again. The cache system generates a static HTML file and saves. Other users reach to static Html page.