Talking about the domain registration is something really interesting. What will we have after the domain is register? How to make the domain know where is the hosting server?
These two questions are really good question. Let me start by answering the first question. After you did the registration, you will receive an account which is used to manage your domain such as your personal information, domain information, and other information based on the features of each Registrar giving to you. With that account, you will also be able to change the DNS of the domain to let it know where the hosting server is. This is the answer for the second question. In short, account for managing the domain is very important once you change often the hosting server.
This is what beyonds the domain registration,
Note: Registrar is organization which provide domain registration. We, the one who register the domain to be it owner, are called domain registrant.