Okay kiddo, so have you ever seen a big book with a bunch of names in it, like a phone book or address book? Well, a mail table book is kinda like that, but instead of people's names and phone numbers, it has information about something called emails.
You see, when you use your computer or phone to send an email to someone, that email has to travel through something called the internet to get to the other person's inbox. But, there are lots of different things that make up the internet, kinda like roads and highways do for cars.
So, the mail table book is like a map that tells your computer or phone which "road" or pathway to use to get your email to the right place. It has lots of different addresses and codes that it uses to help your email find its way to where it's supposed to go.
Without the mail table book, your email might get lost or go to the wrong place, just like if you didn't use a map when driving somewhere new. So, in a way, the mail table book helps make sure everyone's emails get where they're supposed to go, just like a map helps make sure you get to where you're trying to go.