We pick b.root-servers.net, one of the 13 root servers (1), and ask it about sk-nic.sk and learn that sk is delegated to eight name servers (2), so we ask ns.uu.net and get the following answer:
Sk-nic.sk is a domain controlled by three domain name servers at isc.org and tld.sk having a total of six IP numbers. All six of them are on different IP networks. Incoming mail for sk-nic.sk is handled by two mail servers at sk-nic.sk and swan.sk. Both are on the same IP network. Sk-nic.sk has two IP numbers (2a02:770:100:100::106, 195.12.159.5). Both are on different IP networks.