This plugin creates static html files from your dynamic WordPress blog. When a page is rendered, php and mysql are used. Therefor, 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. 

To install:

* Upload wp-fastest-cache to the /wp-content/plugins/ directory
* Activate the plugin through the 'Plugins' menu in WordPress
* Permission of .htacces must 644
* Enable this plugin on option page