# Domain Name Structure

🌐 **Overview** Any given domain name has three primary parts, each serving a specific purpose.

## 1. TLD (Top Level Domain)

The TLD, or top-level domain, is the last part of a domain name. In the example of [www.google.com](http://www.google.com), the TLD is "com." TLDs are predefined and restricted, but their number has been increasing in recent years. Common TLDs include .com, .net, .edu, and country-specific ones like .de for Germany or .cn for China. Some vanity TLDs, such as .museum or .pizza, are also available. ICANN (Internet Corporation for Assigned Names and Numbers), a non-profit organization, handles the administration and definition of TLDs.

## 2. Domain

The domain refers to the second part of a domain name, such as "google" in our example. Domains demarcate control from the TLD name server to an authoritative name server. They are typically under the control of independent organizations or individuals outside of ICANN. Domains can be registered and chosen by individuals/companies but must end with one of the predefined TLDs.

## 3. Subdomain

The subdomain, in this case, "www," is an optional part of the domain name. It can also be referred to as a hostname if assigned to a single host. Combining all parts together, a fully qualified domain name (FQDN) is formed.

✨ **FQDN (Fully Qualified Domain Name)** A fully qualified domain name represents the complete domain name structure. It consists of the subdomain (e.g., www), followed by the domain (e.g., google), and the TLD (e.g., com).

🔒 **Registration and Control** Registering a domain with a registrar involves a cost, but subdomains can be freely chosen and assigned by those who control a registered domain. Registrars are companies authorized by ICANN to sell unregistered domain names.

🔢 **Domain Name Limitations** While DNS technically supports up to 127 levels of domain in total for a single FQDN, fully qualified domain names with that many levels are rare. Additionally, there are restrictions on the length of each individual section, limited to 63 characters, and the total length of a complete FQDN, which is limited to 255 characters.

Remember, understanding the structure of domain names is crucial for managing and navigating the internet. 🌐
