A domain is a distinct section of the Internet with addresses sharing a common suffix or under the control of a particular organization or individual. It is hierarchically organized. Both physical as well as virtual objects can be addressed with the domain name. These objects can be websites, computers on a network, or services, such as printers, faxes or mail servers.

Each object is referenced by a unique IP address, but is included in the namespace, in other words, a domain for the purpose of distinctness and clarity. A domain may consist of letters from A to Z, the numbers 0 through 9, hyphens (only in certain places) and other characters from the Unicode character set.

General information

If a user wants to reach a website, he can enter the IP address of the web server if he knows it. But, because IP addresses are difficult to remember and users have no clue as to what the address represents, the Domain Name System (DNS) was introduced. This system has significantly increased the usability of the Internet in general and of individual websites, since users can now access resources even if they don’t know the IP address. Each domain must be based on this global naming system.

Strictly speaking, the DNS is organized as a hierarchical tree structure. The starting node is the root directory, which is located on the server along with other HTML documents and scripts.[1]

However, this directory is not visible to users. It is only noted internally within the system. The visible parts of a domain are of more interest to users. These are in turn part of the URL, but not to be confused with it. A URL may also point to individual files on the server. A domain includes all files in their entirety. The domain is a range of addresses and the URL is an address.


The domain is divided into three visible parts and an invisible part according to the DNS. The individual parts are syntactically separated by a period.
  • .com denotes the top-level domain. It is either a country code or an indication of the function of the domain (for example, .com for commercial, .biz for business or .org for organization). Recently, even city names are available as domains, such as .london.
  • sample is the 2nd level domain. This is the actual namespace of the domain.
  • www. denotes the 3rd level domain. Special services can be listed here as well, for example, blog. for a blog or mail. for a mail server. Further division into subdomains can map departments of a global company for example.
  • The invisible part is the root directory, which is located on the web server. This is indicated by a period after .com., but is not visible in the Web browser. The period is used to uniquely reference the object on the server, making it a fully qualified domain name (FQDN).

Importance for search engine optimization

Domains have a very high status in the field of SEO and several aspects are significant here.

1. The namespace of a domain can contain keywords and is therefore an important criterion for ranking and users successfully finding what they are searching for. (See Exact Match Domain (EMD))

2. If the abbreviation www. is omitted from the top-level domain, it is also advisable to avoid duplicate content. Sometimes the same content is accessible under two domain names.

3. Under .de for example, you can only reach addresses exclusively from Germany. If you want to target international customers, it is recommended to either have subdomains with the relevant country abbreviations or an appropriate functional addresses such as .com. Moreover, there are aspects to be mentioned that relate to the age, backlinks, reputation, and the neighborhood of a domain. The keywords are domain popularity, domain authority, domain trust, and bad neighborhood. These various aspects are indicators of the quality of a domain and affect the success of a website significantly.


  1. Domain Name System (DNS) Accessed on 07/04/2014

Web Links