The WP Super Cache plugins store dynamically-generated WordPress posts and pages as static files. These static files are then served to users, significantly reducing the processing load on the server and accelerating page speeds.
Cached files will be served to the majority of your readers. Three caching modes are available to support a range of administration skills and goals:
i) Expert Mode uses Apache’s mod_rewrite feature to serve “supercached” static html files and is the fastest mode available. Expert mode completely bypasses PHP and is extremely quick.
ii) Simple Mode is the recommended setting for WP Super Cache and is easier to configure and manage. It’s almost as quick as using mod_rewrite, but does not require .htaccess changes.
iii) WP-Cache Caching is used to cache pages for known users (i.e. logged in users and visitors who leave comments). This mode is always enabled, but can be customized depending on your needs.