Fondamentalement, c'est what le name says it is. An authoritative answer comes depuis a nameserver that is considered authoritative for le domain qui c'est returning a record for (one of le nameservers in le list for le domain you did a lookup on), et a non-authoritative answer comes depuis anywhere else (a nameserver pas in le list for le domain you did a lookup on).
C'est basically a distinction entre a nameserver c'est an official nameserver for le domain you're querying, et a nameserver that isn't. Nameservers that ne sont pas authoritative are getting leur answers second (or third ou fourth...) hand - juste relaying le information along depuis somewhere else.
So, par exemple, If I did an nslookup of maps.google.com right now, I would get a response depuis one of mon configured nameservers. (Either depuis mon ISP, ou mon domain.) It would come back as non-authoritative parce que ni mon ISP's nameservers, nor mon own are in le list of nameservers for google.com. They ne sont pas Google's nameservers, so they're pas le authoritative source that creates le NS records.
The list of authoritative nameservers for Google is ci-dessous (from whois.internic.net).
Domain Name: GOOGLE.COM
Registrar: MARKMONITOR INC.
Whois Server: whois.markmonitor.com
Name Server: NS1.GOOGLE.COM
Name Server: NS2.GOOGLE.COM
Name Server: NS3.GOOGLE.COM
Name Server: NS4.GOOGLE.COM
Updated Date: 20-jul-2011
Creation Date: 15-sep-1997
Expiration Date: 14-sep-2020
If I changed mon configured DNS server to one of le ones in that list, et alors did an nslookup against maps.google.com, J'aimerais get an authoritative answer back. Those servers are le authority, (or source) for what are valid names in Google's domains, et what aren't. All autre nameservers, non-authoritative nameservers, get leur NS records depuis le authoritative servers somewhere down le line.
