Okay, so let's imagine you're making a little sandcastle at the beach, and suddenly you see a big, mean bully come up and kick your sandcastle over. You feel really angry and upset, right? Well, in some places in the world, people feel very angry and upset about something that happened a long time ago. They believe that a long time ago, a big, scary devil came and tempted some important people to do bad things.
Now, because they believe that the devil is responsible for these bad things, they want to show how angry they are at him. So they come together in a big group and they pretend to throw little stones at him to show they are mad. But here's the catch: they are not actually throwing stones at a real devil! They are throwing stones at little pillars that are meant to represent the devil. This is called "stoning the devil," and they do it every year to show how angry they are at the devil for tempting people to do bad things.
It might sound a bit strange or scary to you, but for the people who believe in it, it's an important way to show their faith and their anger at the bad things that happen in the world.