fortios config backup - can someone help me understand this please

[Gisbert Haas]

https://docs.ansible.com/ansible/latest/collections/fortinet/fortios/fortios_system_config_backup_restore_module.html

using the example from the documentation above

I dont understand why hosts is set to locahosts and I need to specify a host with its IP.

hosts: localhost 

   connection: httpapi 

    collections: - fortinet.fortios 

     vars: vdom: "root" 

       host: "192.168.122.60"

usually the hosts are in the hosts file but when I change 

hosts: localhost 

to 

hosts: fortigates for example  and remove the host entry the playbook will not run anymore.

Thanks