Each machine on the Internet has an IP address.  To make contact with the other machine you need to know the IP address of the machine in question.  Since people find names easier to remember than they do numbers, it is sensible to associate each IP address with a symbolic name.  A domain name is much simpler than an IP address which consists of 32 bits.  The combination of digits and full stops is unique, not two machines have the same IP address.  That is also why your domain name is unique.

By means of the domain name, you have the opportunity to make yourself known on the internet.  You can choose for example your personal name, the name of your business or your trademark.  So why hesitate?  Register your domain name now!