Raster based density calculations represent a type of interpolation.The ArcGIS manual overview of the Density toolset states, "calculating density, you are in a sense spreading the values (of the input) out over a surface". The section of the ArcGIS manual on Understanding Density Analysis states, "[t]he Density tool distributes a measured quantity of an input point layer throughout a landscape to produce a continuous surface." Calculating density is not the same as generating topography from point elevations, but both density and topographic rasters represent an array of discrete points as a field of values. Thus, in a very general sense one can think of Density as a type of spatial interpolation.
ArcGIS provides three Density tools: Kernel, Line, and Point. Kernel densities produce tapered surfaces. Line and Point densities produce magnitude per unit area within the radius of each cell. The two figures below illustrate Point Density and Kernel Density surfaces generated from the same feature classes, that are in this case archaeological sites. Densities can be generated on just about any kind of point or line feature.....
from Geoprocessing | Scoop.it http://www.scoop.it/t/geoprocessamento/p/4012877665/2013/12/18/lab-6-density-analysis-anthropology-analytical-cartography-lab-confluence