To understand why you need a domain name you first need to know how a domain name works.
A domain name is an addressing construct, used for finding and identifying computers on the Internet. Computers use Internet Protocol (IP) Addresses, which are a series of numbers used to identify each other on the Internet; however, many people find it hard to remember IP Addresses. Because of this, domain names were developed so that easily remembered names and phrases could be used to identify entities in the Internet instead of using an IP Address.

For example, the domain name web-sketchers.com identifies the company web-sketchers.com. When a user types the domain name web-sketchers.com in their browser or sends an email to web-sketchers.com, the Domain Name System (DNS) will translate the domain name into IP numbers. These are then used by the Internet to connect the user to web-sketchers.com’s web presence.