A bump map is used to simulate roughness on a surface. Bump maps are grayscale images where dark gray/black signifies lower areas and bright white/light gray areas signify higher areas. They work by shifting the object’s normals to give the illusion of depth. On a human figure, a bump map allows you to simulate wrinkles and other imperfections/textures.

Bump maps use the same template as texture maps in order to properly fit your figure/prop:

Please refer to Part 2 of your Poser Reference Manual for more information about maps.