Imagine you have a toy car and you want to play with it on the road. But the people who take care of this road, they also need money to keep the road nice and safe for everyone who uses it. So they ask you to pay some money so that you can play with your toy car on the road.
Similarly, when people drive their real cars on the roads, they have to pay something called the road tax or vignette. This is like the money that you paid for your toy car road. The government uses this money to take care of the roads, fix any damages or problems, and keep the roads safe for all drivers.
A vignette is like a sticker or a piece of paper that shows you paid this road tax. You stick this vignette on your car's windshield so that the police and other authorities can see that you already paid the road tax. If you don't have a vignette, you can get a fine or even get your car towed away!
So, in short, a vignette is a kind of payment that drivers have to make so that they can use the road, and it's like a sticker that shows you paid this payment.