Every server in the world that has access to the Internet has at least one IP address -- to a computer, this is like a phone number. An example of an IP address is 220.127.116.11.
Instead of having to remember a bunch of numbers, domain names allow us to assign a name to those numbers. Without domain names, you would have to enter an IP address every time you wanted to visit a website. Isn't google.com much easier to remember than 18.104.22.168?
Domain names can contain letters, numbers, and hyphens. They can be hundreds of characters in length, but the shorter the domain, the better.
This picture shows an example of why very long domains are a bad idea. More on this in the next tutorial.
In order for your computer to figure out what IP address to use for a domain name, it has to connect to a nameserver, also called a DNS server. That server connects to another server, which connects to another, and so on, until a server is encountered that knows the right IP address for the domain name.
When you purchase a domain name, you then tell the domain registrar that all requests for an IP address for that domain name should be directed toward your hosting provider's nameservers.
You'll find out more about domain registrars and how to buy a domain name a few tutorials later in this series.
Once you've informed your web host the domain you plan to use, they'll configure their nameservers to give your domain name a specific IP address.
Usually you'll share an IP address with many other domain names. You can also purchase a dedicated IP address from your web host, and that will be yours alone to use. Whichever the case, the important thing is that you have an IP address assigned to your domain, and that all the right nameservers know what it is.
This completes the tutorial. You now know what domain names are, and a little bit about how they work.