Quote - What is the difference between a Displacement map and a Normal map?

Normal mapping manipulates the surface normals of a model, creating the illusion of a higher-resolution, more detailed mesh through shading effects.  It does not actually increase the mesh resolution or displace the geometry, however, and this is usually obvious by looking at the model's silhouette.  The edges remain unchanged.

Poser's displacement mapping actually displaces the geometry, creating real indentations or raised surfaces, with micropolygon subdivision at render-time to permit such higher detail.

Normal mapping is less computationally-intensive than displacement mapping, which is why it is more commonly used in real-time applications like games.