This article is a copy of a section from “Domain Name“
There are four parts to a domain. The prefix/protocol, the subdomain, the domain, and the suffix.
The protocol is the part of the domain that shows which communication method our computer uses to connect to that website. The most common protocol you have probably heard of is HTTP (Hypertext Transfer Protocol) or HTTPS (Hypertext Transfer Protocol Secure)
Some other protocols that you may be familiar with are:
A subdomain is a website under the main domain. A subdomain is the only optional part of domain. One interesting fact about subdomains is that they can go up to 127 layers deep. (ex: etc.threelayer.twolayer.onelayer.domain.com)
Some examples of subdomains:
A domain name is considered to be made of two parts. The domain name itself and the extension. (Which is discussed next)
A domain name is a unique identifier for a website on the internet.
An extension is what follows the domain name itself. A common extension is the .com extension. Nowadays, there are so many new domain extensions for almost all types of businesses or organizations.