About making a kid

[Demo]

I am trying to make a backup of final fantasy X, but I have a problem or I don't understand how the kid fully works, or what it is exactly for.

For what I have understood you make the kid and then copy it in a cd. But what is the purpose of that cd, it only takes 7 MB of memory, it can not be the game.

Is it to be able to copy the game or what?

Can someone please help me little, I am confused.

Thank you, greetings.