Configuring sites/urls on a Nginx web server

Notes that accompany this video:
https://codewithsusan.com/notes/nginx-sites-config

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=== SUMMARY ===
Let’s learn how to configure a new site/URL on a Ubuntu server running Nginx. As an example, I’ll configure a site via the URL http://demo.codewithsusan.com. I’m using a subdomain for the example but the same procedures apply for a primary domain.