When a page is rendered, php and mysql are used. Therefore, system needs RAM and CPU.If many visitors come to a site, system uses lots of RAM and CPU so page is rendered so slowly.
In this case, you need a cache system not to render page again and again. Cache system generates a static html file and saves. Other users reach to static html page.
Discover the features of WP Fastest Cache Premium Nulled and be aware the difference with other plugins.
GIPHY App Key not set. Please check settings