According to United Domains, domain structure consists of information to the left of the period and the letter combination to the right of it in a Web address. The content to the right of the punctuation is the domain extension, while the content on the left of the punctuation is the domain name.
The domain structure can be broken down into top-level domains (TLD), or first-level domains, and sub-Level domains (SLD). The most common TLDs include .com, .info, .org and .net. A TLD is also sometimes represented as a country code such as .us, .ca and .de. SLDs are domains that are created in order to connect a related page to the main website. SLDs are subdivisions of a TLD that represent the specific product, service, organization or business. They direct someone to a specific part of an existing website and eliminate the need to register a completely separate domain.
One of the best things about domain names is that they are unique. This uniqueness is also what makes some domain names quite valuable. A new domain name is recorded in a database, and each record in the database must be unique. The owner and registrar of a domain name are found through directories such as WHOIS.com.