The upstream directive in Nginx is used to define a group of backend servers that can be used for load balancing. In the provided example, a backend server is specified with its IP address and port.

upstream app_front_static {
    server 192.168.206.105:80;
}

In this configuration:

  • app_front_static is the name of the upstream block, which can be referenced in other parts of the Nginx configuration.
  • The server directive specifies the backend server's address and port that Nginx will forward requests to.

This setup is useful for distributing traffic among multiple servers to improve performance and reliability.