OK, this is still a work in progress, but with Digital Ocean, the main site for https://tongfamily.com (also accessible as https://droplet.tongfamily.com as https://richtong.org) is cool because it runs in its own virtual server. In contrast, our Bluehost image (https://bluehost.tongfamily.com or https://richtong.net) runs with Cpanel.
In the Cpanel case, you can create an unlimited number of WordPress sites through their domain administrator. Each is served out of a directory. The charging structure is a fixed monthly price for an unlimited number of sites.
However with Digital Ocean, we have a virtual server which they call a Droplet (or AWS would call an EC2 instance). And the charging structure is per droplet, so it would be great to have an apartment model so you don't run up big charges for low volume websites.
There is a way to do this called WordPress MU or Multiuser. But since version 3.0, they have integrated it into core WordPress and you now create a "network of sites"
The first step is to download a new droplet with the WordPress image and then at the spot in
/var/www/html/wp-config.php you want to add the lines. You will need either an FTP editor or SSH access to do this
/* Multisite */ define( 'WP_ALLOW_MULTISITE', true );
Then you just refresh the browser and you are off and to the races. The big fork in the road is whether you are using subdomains to define your sites, so their natively live in
https://yoursite.com/site1 and so forth or
https://site1.yoursite.com which is what is called the subdomain setup
Then you need to define your network which means more changes to wp-config.php and your .htaccess