Okay kiddo, so back in the olden days before we had phones, computers or even email, people needed a way to send messages to each other that were far away. That's where the telegraph comes in!
A telegraph is a machine that sends messages over wires with special codes that use dots and dashes. And a telegraph boy was the person who brought these messages from one place to another.
So let's say your grandpa lives in a different city and you want to tell him something important. You would go to the telegraph office and tell the telegraph operator what you want to say. The operator would then use the telegraph machine to send the message in code over the wires.
But how would the message get to your grandpa if it's just code on wires? That's where the telegraph boy comes in! He would go to your grandpa's house with the message, read it out loud to him, and then take any message your grandpa wanted to send back to you.
So the telegraph boy was like a messenger, delivering important messages between people who were far apart. It was a very important job back then because it was the only way people could communicate quickly over long distances.