What is backendserver-address?

[Thatoo]

I have a question about https://github.com/ONLYOFFICE/document-server-proxy/blob/master/nginx/proxy-https-to-http.conf

For me, docservice in
proxy_pass http://docservice;
is the local ip address
it looks like
proxy_pass http://xxx.xxx.xxx.xxx;

but I don't understand what should be backendserver-address in
upstream docservice {
server backendserver-address;
}

should it be the same IP adress
upstream docservice {
server xxx.xxx.xxx.xxx;
}

or docservice and backendserver-address are different?

[PulsarFX]

it worked for me with the name of the hosting server, like

  upstream docservice {
    server myserver:8881;
  }

where I started docker using 8881:80 mapping