Default main webserver for your server
The Apache2 webserver serves as a proxy for NGINX
By default, ploi.io installs your server with the NGINX webserver. However this webserver is not compatible with .htaccess, this is where the hybrid function is for. (Oh, and WordPress runs just fine with NGINX only)
If you are in real need of .htaccess support you can consider installing the hybrid option when installing a new server.
The only downside is that this takes up a bit more resources because you are running 2 webservers at the same time.