Unlike bump and normal maps, a displacement map affects the geometry of a model. This means that the polygons are moved, displaced, from their original position. For example, if we have a model of a car, a displacement map can move the polygons in it to simulate the effect of a collision, or a rock hitting the side of the car.
The effect is achieved with a map that is very similar to the bump map. A grayscale texture that indicates positive or negative displacement at several points. The dark spots indicate dents, and the light spots in the map will move the geometry “up,” along the normals.