Domain Name :
This is the name that identifies a Web site. For example, "microsoft.com" is the domain name of Microsoft's Web site. A single Web server can serve Web sites for multiple domain names, but a single domain name can point to only one machine. For example, Apple Computer has Web sites at www.apple.com, www.info.apple.com, and store.apple.com. Each of these sites could be served on different machines.
Then there are domain names that have been registered, but are not connected to a Web server. The most common reason for this is to have e-mail addresses at a certain domain name without having to maintain a Web site. In these cases, the domain name must be connected to a machine that is running a mail server.
Name Server :
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A name server translates domain names into IP addresses. This makes it possible for a user to access a website by typing in the domain name instead of the website's actual IP address. For example, when you type in "www.microsoft.com," the request gets sent to Microsoft's name server which returns the IP address of the Microsoft website.
Each domain name must have at least two name servers listed when the domain is registered. These name servers are commonly named ns1.servername.com and ns2.servername.com, where "servername" is the name of the server. The first server listed is the primary server, while the second is used as a backup server if the first server is not responding.
Name servers are a fundamental part of the Domain Name System (DNS). They allow websites to use domain names instead of IP addresses, which would be much harder to remember.
Domain Name System
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The Internet maintains two principal namespaces, the domain name hierarchy and the Internet Protocol (IP) address system. The Domain Name System maintains the domain namespace and provides translation services between these two namespaces. Internet name servers implement the Domain Name System. A DNS name server is a server that stores the DNS records, such as address (A) records, name server (NS) records, and mail exchanger (MX) records for a domain name and responds with answers to queries against its database.
The top hierarchy of the Internet Domain Name Server is served by the root name servers maintained by delegation by the Internet Corporation for Assigned Names and Numbers (ICANN).
Top-level domain :
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A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a fully qualified domain name. For example, in the domain name www.example.com, the top-level domain is com, or COM, (domain names are not case-sensitive). Management of most top-level domains is delegated to responsible organizations by the Internet Corporation for Assigned Names and Numbers (ICANN), which operates the Internet Assigned Numbers Authority (IANA) and is in charge of maintaining the DNS root zone.Originally, the top-level domain space was organized into three main groups, Countries, Categories, and Multiorganizations. An additional temporary group consisted only of the initial DNS domain, arpa, intended for transitional purposes toward the stabilization of the domain name system.
Root domain
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The Domain Name System is a hierarchical naming system for computers, services, or any resource participating in the Internet. The top of that hierarchy is the root domain. The root domain does not have a formal name and its label in the DNS hierarchy is an empty string. All fully qualified domain names (FQDNs) on the Internet can be regarded as ending with this empty string for the root domain, and therefore ending in a full stop character (the label delimiter), e.g., www.example.com.. This is generally implied rather than explicit, as modern DNS software does not actually require that the terminating dot be included when attempting to translate a domain name to an IP address.
The root domain contains all top-level domains of the Internet.
