Understanding Top Level Domains, Second Level Domains and Sub-domains for Beginners

It can be difficult to understand the different types of domain names. You may be surprised type of domain you may be registering. Here we will try to demystify domains. What is the difference between a top level domain, a second level domain, and a sub-domain.

What is a Domain Name (DN)

A domain name comes from real estate where a domain refers to a territory or an area controlled or owned by a specific entity. That could be a government, a business, or a private individual. It is related to the word dominion, which has the idea of power or control over land. A domain name aptly refers to an area of the Internet where someone builds something, a website, as you would build a house on a piece of land you control. And as building out physical land requires the coming together of many different skills, materials, equipment, etc., so there are many moving parts that come together in order to develop a domain into a website. Fortunately, companies have made this not much of a concern as they handle many of those details for us behind the scenes. But that is a topic for another article.

Here we will try to dissect domain names. It can be a little confusing for the uninitiated. This is because a domain name that you register is actually made up of at least 2 distinct domains. To help you understand that, lets consider the most common domain, the top level domain.

Top Level Domain (TLD)

As the name indicates, this is the most important domain in the hierarchy of the domain name structure. This is what you see on the right side of the dot, also referred to as extensions. So that would be .com, .net, .org, .info, etc. You may also heard expressions such a generic top level domain, a new generic top level domain, and country code top level domain domain.

You cannot register a top level domain, or a TLD. Those are managed by registries, who maintain a database of registered domains in the TLD they control. For example, the .com TLD is managed by Verisign. Country code TLD’s are maintained by registries under the supervision of various countries. So .ca is managed by CIRA, a governmental agency. And other countries have set up similar supervisory or regulatory organizations. New generic TLDs operate in much the same way as the legacy TLDs with other registries controlling them. New generic TLDs are not country specific which include such extensions as .xyz, .online, .company, .coffee, etc., and there are hundreds of these TLDs.

Second Level Domain (SLD)

This is the part you register and have control over. Second level domain is the part on the left side of the dot. When you register a domain, you pick from the available list of TLDs, and then you decide what word(s) will go on the left side, if available, if someone else hasn’t already chosen it. This becomes your personal individual domain name since only one person can register that particular sld.tld combination.

Sub-Domain (SD)

Once you have registered a domain name, then at the hosting service you are able to create sub-domains. How many is only limited by the hosting plan you purchased. A sub-domain add another dot to the left side of your domain name, sd.sld.tld. So companies have created sub-domains like support.companyname.com or contact.companyname.com.

As you can see, each dot separates the levels of the domain name. The TLD is the root. You cannot have just a TLD. You must register it with the second level, SLD. Then you are able to create your own sub-domains, or the third level. But the third level is only optional and not necessary to start using your domain name. Search engines consider sub-domains as separate from the primary domain name. So this gives you the freedom to create a separate website on a sub-domain if that makes sense. Or you can just go and register different domain names for new websites.

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