Introduction 

What is Domain Name (Domains)

The domain name system (DNS) stores and associates many types of information with domain names (domains), but most importantly, it translates domain names [domains] (computer hostnames) to IP addresses. It also lists mail exchange servers accepting e-mail for each domain. In providing a worldwide keyword-based redirection service, DNS is an essential component of contemporary Internet use.

 What is in the Domain Name (Domains)

 Each string of letters, digits and hyphens between the dots is called a label in the parlance of the domain name system (DNS). Valid labels are subject to certain rules, which have relaxed over the course of time. The original rules state that labels must start with a letter, and end with a letter or digit; any intervening characters may be letters, digits, or hyphens. Labels must be between 1 and 63 characters long (inclusive). Letters are ASCII A–Z and a–z; domain names (domains) are compared case-insensitively. Later it became permissible for labels to commence with a digit (but not for domain names [domains] to be entirely numeric), and for labels to contain internal underscores, but support for such domain names (domains) is uneven. These are the rules imposed by the way names are looked up ("resolved") by DNS. Some top level domains (domain names)(see below) impose more rules, such as a longer minimum length, on some labels. Fully qualified domain names (domains) (FQDNs) are sometimes written with a final dot.

Examples of Domain Name 

The following example illustrates the difference between a URL (Uniform Resource Locator) and a domain name:
URL: http://www.example.com/
Domain name: example.com

As a general rule, the IP address and the server name are interchangeable. For most Internet services, the server will not have any way to know which was used. However, the explosion of interest in the Web means that there are far more Web sites than servers. To accommodate this, the hypertext transfer protocol (HTTP) specifies that the client tells the server which name is being used. This way, one server with one IP address can provide different sites for different domain names (domains). This feature goes under the name virtual hosting and is commonly used by Web hosts.

For example, the server at 192.168.0.5 handles all of the following sites:
example-a.com
example-b.net
example-c.org

When a request is made, the data corresponding to the hostname requested, is served to the user.