Lets say you have a website, how can people reach it? One answer is, by entering your website address (or “URL” in nerd-speak) into your browser's address bar. A website has to have a unique address so that it can be found. Just as real world home addresses are unique to avoid confusion, website addresses have to be unique also.
How do you get a unique address? By registering a domain name. Examples of domain names are “ibm.com” and “wikipedia.org”. Our domain name is “helpsme.com”. The helpsme.com domain name is mapped to the server that stores the files that makes up this website.
An organization named ICANN coordinates these domain names across the world. This is necessary so that when you type an address into your browser, you reach the website you were looking for.