If it's an internal website then yes, you can call it whatever you want. website.vl, website.zzz. BUT, if you want people from the internet to access it with a name to remember, then you will need to register a proper domain name. You don't really need to have name and can make your own website with an IP address. But if you do that, nobody will remember the exact IP address, and it may change if your ISP gives you a dynamic IP address. You can use what they call a dynamic DNS which will update your dynamic IP address to a fixed name.
Nothing is hard, per se, once you understand it. I suggest you read up more on DNS