Let's get a few terms out of the way.
Top level domain: A top level domain, or TLD, is the very
last part of a domain name. The most well-known TLD is
.com,
for commercial businesses, but there's also:
- .org for non-profit organizations
- .net for network providers
- .edu for educational institutions
- .gov for government agencies
- .mil for military branches and agencies
- .int for international organizations
Those are called
generic top level domains, or gTLDs. Additionally,
every country has its own two-letter
country code top level domain,
or ccTLD, that it can use as it pleases. For example:
- .ca for Canada
- .jp for Japan
- .us for the United States
- .uk for the United Kingdom
- .de for Germany
- .va for Vatican City
Hostname: This is the name of a computer, usually the name
of a server. Frequently, servers that perform certain common functions
are given standard names according to convention (
www for a Web
server,
ftp for an FTP server,
mail for an e-mail server,
ns1 and
ns2 for primary and secondary DNS servers
respectively, etc.). However, this is only convention; there's no rule
about what your hostnames have to be. Mindspring's DNS servers are
named
itchy and
scratchy, which I personally think is
very cool.
Fully Qualified Domain Name (FQDN): This is a long annoying
term that just means the combination of a hostname and a domain, such
as
www.ibm.com,
bbs.ufies.org,
www.apple.co.jp,
mail.webwizardry.net, etc. It's also possible for a domain name
to also be a FQDN; you aren't required to have a separate hostname. For
example,
phroggy.com is a FQDN by itself, although
www.phroggy.com is another FQDN that points to the same IP address.
Nameserver: Another name for a DNS server. It takes
a name, finds the IP address associated with that name, and gives you the
IP address.
Authoritative: A DNS server that's registered as being
responsible for knowing the contents of a domain. For example,
ns2.slickhosting.com is one of the DNS servers that's authoritative for
webwizardry.net, because it's listed as one of the DNS servers
on the webwizardry.net domain registration.
Root nameserver: One of the thirteen DNS servers scattered
around the globe that are responsible for knowing what servers are
authoritative for the various top level domains. The master root
nameserver, a.root-servers.net, is operated by Network Solutions, and
broadcasts all its information to the other twelve root namservers.
Generic TLD server: Like the root nameservers, these are
scattered around the globe and Network Solutions operates a.gtld-servers.net.
The gTLD servers are authoritative for the .com, .net, .org, .edu domains,
and possibly others as well (I'm not entirely sure).
Registrar: The company that you can register a domain through.
This is the company that takes your money when you register, and is who you
contact if you need to make any changes to your registration information
(such as switching to different authoritative DNS servers). This is
not the company that you give the IP address of your Web server to!