From the interwebs:
"Cavity and Ambient Occlusion maps are specialty textures that can be generated in ZBrush using the masking tools. Cavity maps are essentially the blue channel of a normal map and represent dark shading in the crevices of the model. They can be useful as a multiply layer over a diffuse color map to accentuate details or as a diffuse map in Maya to help punch up the high-frequency details in a render. Figure 9.67 shows a cavity map. It is essentially a black-and-white map in which black represents the recesses and white is the high points.
Cavity mapping is intended to help mimic Ambient Occlusion, but it is not by nature an Ambient Occlusion effect. It also has several other uses. Ambient Occlusion works by casting rays out from the surface of a 3D model. If a ray hits another surface before dying out, then a grayscale value is recorded that represents how far that ray traveled before being occluded. This is how Ambient Occlusion maps generate darker shadows in tight recesses like inside ears or under the brow ridge."
If i understand right, this quote is saying that a cavity map is just a “painted on effect”, whereas an AO map will actually interact and change the shading depending on the angle it is viewed from? Or is AO also just a painted on effect? So, not interactive, in the same way as a bump or normal map?