Normal maps: Normal maps are maps of the 3D modelling using colors consisting of red, green and blue. These RGB values translates to x, y, and z coordinates, allowing a 2D image to represent depth. This way, a 3D application is able to fake lighting details based on the color associated with the 3D coordinate.A normal map is commonly used to fake high-resolution details on a low-resolution model.
Displacement: Displacement mapping is an alternative technique to bump mapping or normal mapping. It uses a procedural texture or height map to cause an effect where the actual geometric points over the textured surface are displaced. It gives the surface a great sense of depth and detail.
Bump Maps: Bump mapping is a technique in 3D modelling for creating bumps and wrinkles on the surface of an object. This is done by changing the textures of the model to Black and white. The white parts of the surface are raised, and the black parts are lowered. Unlike displacement mapping, it does not change the actual surface area of the object.
Thomas Boiston 