A quick look at height maps
These kind of texture maps store information in the white and black colour values corresponding to the distance the surface of the model gets displaced, usually 100% white (0% black) would displace the geometry furthest distance in the normal direction while 0% white (100% black) would not displace at all being black a value of 0. However we need to point that some software use 50/50 grey as 0 therefore black would have a negative value displacing the geometry in the opposite direction of the face normal.
Below we can see a height map of an Hex grid.
HP Reveal does not use displacement maps at this point however we can use the height map to produce a normal map, which will not displace physically the geometry, but will produce a light effect that will give us the appearance of geometry detail in a low poly surface.