Questions about blender's Bake feature under the Render panel, such baked images as normal maps, AO maps, and displacement maps, and texture maps.
Precomputed maps These maps, such as normal maps, ambient occlusion (AO) maps, and displacement maps, represent different values of a model or scene. The maps are baked onto images that can be saved and loaded at render time so that the computation of the value (normal, AO, displacement, etc.) doesn't have to be performed again every render. In the image file, each pixel represents the value for the matching UV coordinate.
Physics simulations For physics simulations, use the baking tag.