Three Levels of a Domain Name

A domain name is the name of a particular website. For example, the site you are just reading is http://www.bukisa.com. Do you know how many parts a domain name actually has? Do you know which type of domain names are preferred by the Google AdSense Team?


THREE PARTS OF A DOMAIN NAME
A domain name consists of three parts technically called labels, that are conventionally concatenated, and delimited by dots, such as example.com.

• The first part is the word or phrase (right-most label) is the extension. Examples of common extensions include .com, .net or .org. For example, "com." is the second part in my Blog URL http://my-blogging-journey-step-by-step.blogspot.com/
  
• The second portion of the domain name is an optional part. Like the first level domain name, it consists of a word or phrase to describe whatever web page it is pointing to. For example, "blogspot." is the third part in my Blog URL http://my-blogging-journey-step-by-step.blogspot.com/
• The third part of the domain name (left-most label) that makes up the initial domain name. For example, "my-blogging-journey-step-by-step." is the first part in my Blog URL http://my-blogging-journey-step-by-step.blogspot.com/

LEVELS OF A DOMAIN NAME
 The above mentioned parts of a domain name (labels) correspond to the levels of  a domain name

• The right-most label conveys the top-level domain; for example, the domain name www.example.com belongs to the top-level domain com. The top-level domains (TLDs) are the highest level of domain names of the Internet. They form the DNS root zone of the hierarchical Domain Name System. Every domain name ends in a top-level or first-level domain label..There are many types of domain names i.e., the most popular being .com. Other examples are .pk, .au, and .net.
• Below the top-level domains in the domain name hierarchy are the second-level domain (SLD) names. These are the names directly to the left of .com, .net, and the other top-level domains. As an example, in the domain en.wikipedia.org, wikipedia is the second-level domain.Second-level (or lower-level, depending on the established parent hierarchy) domain names are often created based on the name of a company (e.g., bbc.co.uk), product or service (e.g., gmail.com).
• Next are third-level domains, which are written immediately to the left of a second-level domain.
• There can be fourth- and fifth-level domains, and so on, with virtually no limitation.

EXAMPLE OF AN OPERATIONAL DOMAIN NAME WITH FOUR DOMAIN LEVELS

An example of an operational domain name with four levels of domain labels is www.sos.state.oh.us. The www preceding the domains is the host name of the World-Wide Web server. Each label is separated by a full stop (dot). 'sos' is said to be a sub-domain of 'state.oh.us', and 'state' a sub-domain of 'oh.us', etc. In general, subdomains are domains subordinate to their parent domain.

HIERARCHY OF A DOMAIN NAME
The hierarchy of domains descends from the right to the left label in the name; each label to the left specifies a subdivision, or subdomain of the domain to the right. For example:in http://www.example.com/  the label example specifies a subdomain of the com domain, and www is a subdomain of example.com.

 
REQUIREMENT OF GOOGLE ADSENSE
If you apply for Google AdSense account for your blog or website, then they will approve your account only if your Top-level domains

Your website must be your own top-level domain (www.example.com and not www.example.com/mysite).

The top-level domains (TLDs) are the highest level of domain names of the Internet. They form the DNS root zone of the hierarchical Domain Name System.