Okay kiddo, imagine you really like superheroes like Spiderman, Batman, or Superman. These characters are heroes because they do really amazing and brave things and save people from danger. Now, imagine there are people who study stories and myths from a long time ago, like ancient Greece or Egypt. They have found that there are stories about heroes from a long time ago too.
One of these stories is called the "myth of the birth of the hero". In this story, there is a special person who is going to be born, and before they are born, there are some things that happen that show they are going to be a hero. For example, their mom might have a dream that a god told her she was pregnant with a special child, or maybe some animals gather around her when she is pregnant. These are signs that the baby is going to be a hero.
Then, when the baby is born they might have some special things happen like being born in a really unusual way or with a special power like being really strong. This is different from how normal babies are born, and it shows that the baby is going to be a hero.
So, the "myth of the birth of the hero" is a story that talks about how the hero was "destined" to do amazing things from before they were even born, and that there were signs to show they were going to be special. It's a way to explain how some people can become heroes and do things that are really amazing and important.