A subdomain is a subset of a domain name, used to organize and navigate to different sections of a website. A domain name typically consists of a top-level domain (TLD) also known as a domain extension (such as .COM ) and a second-level domain (SLD).

Let's take subdomain.dynadot.com as an example:

• dynadot.com is the main domain (also called the root domain) with "dynadot" as a SLD and .COM as a TLD.
• subdomain is the subdomain.

Please note that a subdomain is not the same as a third-level domain.

Subdomains are configured via DNS so they couldn't be registered as a main domain directly, and they can point to the same or different IP addresses than the main domain.

Want to set up DNS for your subdomains? Please follow this guideline and add the records under "Subdomain Records (optional)":
How do I set up DNS for my domain?