How F-Root Server works?

[Daniel Sadoc]

Hi people,

Please, I would like to understand how the F-ROOT SERVER works.

Is the F-ROOT SERVER a set of machines, all of them responding to the
same IP?

How is the nearest F-ROOT SERVER choosen?

I've found out, for instance, that 

gru1b.f.root-servers.org has the IP 192.228.80.6 while

pao1d.f.root-servers.org has the IP 204.152.184.251.

If the machines above are in different countries, how they respond to
queries for the IP of F.ROOT-SERVERS.NET, which is 192.5.5.241?

Thanks in advance.

Regards,
Daniel Sadoc