Explanation
The root directive in Nginx defines the file system path from which the content of the server is retrieved. It can be placed in the http, server, or location contexts. The root directive specifies the root directory that will be used to search for a file. To obtain the path of a requested file, Nginx appends the request URI to the path specified by the root directive. For example, if the root directive is set to /var/www/html and the request URI is /index.php, Nginx will look for the file /var/www/html/index.php. References: Serving Static Content | NGINX DocumentationUnderstanding and Implementing FastCGI Proxying in Nginx