Hi there! Do you know how sometimes you hear your mom or dad's keys in the door before they actually come inside? That's called a vardøger.
In some countries, people think that before you actually get to a place, your vardøger goes ahead of you to announce your arrival. It's like a kind of ghost or spirit that mimics your movements before you actually get there.
So when someone hears a vardøger, it's like they hear something that hasn't really happened yet. It's kind of like a magical warning that someone is on their way! Cool, huh?