refresher: how DNS works 


  DNS utilizes a hierarchical name space divided into zones that are
  distributed among the name servers. Each zone has one or more
  authoritative name servers responsible for answering queries 
  for names within their zone(s).

  In order to reach a machine with the name not.invisible.net, 
  one must send a query to the DNS server responsible for machines 
  and/or sub-domains in the domain .invisible.net.  

  To find this DNS server, one must send a query to the server 
  authoritatively responsible for .net. Such a server is called a 
  global top-level domain (gTLD) server. To find the appropriate 
  gTLD server, one must query one of the root servers. 
  Currently there are 13 gTLD servers and 13 root servers.