WP Super Cache generates static html files from your dynamic WordPress blog. After an html file is generated, the webserver will serve that file instead of processing the comparatively heavier and more expansive WordPress PHP scripts.
In simple, your website upload times will go down, because the server is processing simpler, smaller files. Your readers will be happy. Especially those ones with smart-phones and dial-up modems.
Follow the link below to know more about the WP super cache:
http://wordpress.org/extend/plugins/wp-super-cache/
