As no two parties may ever hold identical domain names, it is truly a unique identifier of you or your company.
It is how your customers will remember you and find you among the millions of other Web sites on the Internet.
Domain Names always have 2 or more parts, separated by dots.
The part on the left is the most specific, and the part on the right is the most general.
A given machine may have more than one Domain Name but a given Domain Name points to only one machine.