When people make toys or machines that fly, they need to give them a special tag called registration. The same thing applies to real airplanes that fly high in the sky. When people build airplanes that are big and strong, they also need to give them registration so that everyone knows who owns them.
An aircraft registration is just like a name tag that people wear at a party. It shows who the airplane belongs to and also has a unique number on it that no other airplane has. Just like your name and your house address, the airplane's registration helps people identify it and keep track of who it belongs to.
When people buy or sell an airplane, they also transfer its registration from one owner to another, just like when you get a new toy and write your name on it. This way, everyone knows who to contact in case the airplane needs help or needs to be fixed.
In summary, aircraft registration is just like a name tag that shows who owns the airplane and helps keep track of it in case something goes wrong.