What does nginx for Plesk actually do
By Default the system will configure the web server to work as a reverse proxy - nginx becomes a frontend web server that processes all incoming requests from site visitors. The requests are sent to Apache which, in turn, distinguishes requests for static and dynamic content. If a request is for a static file (like jpg, css, html, and so on), Apache passes the request through all registered handlers (applies .htaccess directory-level configuration, rewrites a URL, and so on) and returns to nginx a response which contains only a location of the requested file on the file system. nginx locates the file and sends it to the client. If the request is for a dynamic file (like a PHP script), Apache executes the file and sends the response to nginx, which delivers it to the client.