Context: location. Variables are accepted.

alias is a directive that you place in a location block only. It assigns a different path for Nginx to retrieve documents for a specific request. As an example, consider the following configuration:

http { 
   server { 
       server_name localhost; 
       root /var/www/website.com/html; 
        location /admin/ { 
        alias /var/www/locked/; 
      } 
   } 
}

When a request for http://localhost/ is received, files are served from the /var/www/website.com/html/ folder. However, if Nginx receives a request for http://localhost/admin/, the path used to retrieve the files is /home/website.com/locked/. Moreover, the value of the document root directive (root) is not altered. This procedure is invisible in the eyes of dynamic scripts.

Syntax: Directory (do not forget the trailing /) or file path