File: //usr/share/webmin/virtual-server/help/ssl.html
<header>Set up SSL website too?</header>
When this option is enabled, an additional Apache virtual host will be
created for this virtual server, listening on port 443. This will allow
browsers to connect to https://<i>domainname.com</i>/ using SSL encryption,
as well as to http://<i>domainname.com</i>/ without encryption. <p>
If possible, an SSL certificate from Let's Encrypt will be requesting as part
of the setup process. Otherwise, a self-signed SSL key and certificate will be
generated, so that the SSL virtual host can be immediately used. However, you
should generate a valid SSL certificate for the domain as soon as possible,
so that it can be properly verified by browsers. This can be done on the <b>Manage SSL Certificate</b> page.
<footer>