A serial number is like a special code that gives a unique name to something. Just like how you have a name that only belongs to you, like Sarah or David or Mohammad, there are things like toys, electronics, and cars that have their own special name too.
Imagine you have a toy car that looks just like your friend's toy car. But when you look at the bottom of your car, you see a tiny set of numbers and letters that are different from your friend's toy car. That tiny set of numbers and letters is called a serial number, and it makes your car different and special from your friend's.
Serial numbers are used to keep track of things and help identify them. It's like a secret code that only that one thing has, so if it gets lost or something bad happens to it, people can use the serial number to figure out which thing they are supposed to be looking for. So next time you see some numbers and letters on the bottom of your toys or other things, know that it's your special code that makes your things unique and identifiable!