There are 13 root name servers, they container info about which DNS is authorative (can tell you about) a given TLD (like .com or .de) then that repeats for every part of your query with that given server.

Something. Foo. Bar. Com. (<root name server>) ^ most of the time the same as. ^ DNS for baz or bar dns again ^ DNS for Bar ^ DNS server for the .com tld ^ the one unbound asks first, not part of the domain

The root server ips are known to unbound and static.

---

Then it will ask that server? Like I said unbound remove the middle man and somewhat increases privacy (debatable if only you use it but anyway)