Okay kiddo, so have you ever seen a lighthouse when you go to the beach? It's a really tall tower that shines a big light that helps boats and ships not crash into rocks or other things in the water. That light is called the "leading light."
When boats come in from far away, they can see the leading light shining really bright and it helps them know where to go so they don't get lost or run into anything. It's like a big flashlight that helps them see the way.
Nowadays, some people use the term "leading lights" to talk about people or things that guide us or show us the way in life. So, just like a lighthouse helps boats, leading lights can help us find our way in the world.