A domain name is an identification label that defines a realm of administrative autonomy, authority, or control in the Internet, based on the Domain Name System (DNS). Domain names are used in various networking contexts and application-specific naming and addressing purposes.
They are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, net and org, and the country code top-level domains (ccTLDs).
Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users that wish to connect local area networks to the Internet, run web sites, or create other publicly accessible Internet resources.
The registration of these domain names is usually administered by domain name registrars who sell their services to the public. Well, that's very hard to understand aren't it?
Here's my version of what a domain name is. I like to think of domain name like a person's name in your mobile phone. If you want to ring Karven Tan, instead of typing in my phone number, you can just search for my name in your phone contact list. Then when you hit the call button, your phone dials the number for you.
A domain name is very similar, when you type a domain name into your browser, it rings the IP address of the computer you are trying to reach that hosted that particular website. Instead of using a domain name, you could just print the IP address of the computer that hosts your website onto your business card, but that is a long number that's hard for people to remember.