What is a domain?
The domain (e.g., example.com) is the overarching structure that contains the subdomains (e.g., blog.example.com). For example,
joturl.com are domains.
What is a subdomain?
A subdomain is a domain that is part of a larger domain, for example,
east.example.com are subdomains of the
What is a third level domain?
A third level domain is a specific subdomain that has only 3 parts. For example,
east.example.com are third level domains (and even subdomains) of the
example.com domain, but
go.link.example.com is a subdomain but it is not a third level domain as it has 4 parts (actually it is a fourth level domain).