A displacement map is a technique used in computer graphics to create detailed textures on 3D models. It works by altering the surface of a model based on the brightness values of a grayscale image. Lighter areas of the map push the surface outward, while darker areas pull it inward, giving the illusion of depth and detail. Displacement maps are commonly used in video games and animation to enhance realism without increasing the polygon count of a model. This allows for more efficient rendering while still achieving complex visual effects, making them a valuable tool in the field of 3D modeling and visual effects.