To create sites and place on the Internet, you must buy a domain without which the site can not exist. Domain consists of words often written in Latin letters, of course there are exceptions (for example .հայ).
Domain the Unique Identifier of the Host
Domains are at different levels. For example, a first-level domain cannot be registered by an ordinary user, and a second level cannot be easily registered. Usually, domains of the third, fourth, and other levels are called subdomains.
On the domain name, you can find its specific affiliation.
What is a Subdomain?
A subdomain is part of a higher-level domain name. A subdomain is an extension of an existing domain.
For example mail.hayhost.am, calendar.hayhost.am subdomains of hayhost.am domain.