A parapet is like a little wall that sticks up on the edge of a building or a bridge. Think of it like a fence that stops people from falling off the edge of something high up. The parapet can be made of different materials like bricks, concrete, or metal, and it helps to keep people safe by providing a barrier or a border around the edge of a roof, a balcony, or a terrace. If you look at a lot of buildings or bridges, you can usually spot a parapet on the top of them, and it helps to make the building look more complete too!